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I 29.2: AI 7/EXEC.SUM. 




Report on Effects of Aircraft Overflights 
on the National Park System 






PUBLIC DOCUMENTS 

DEF ■' M 

SEP 2 2" 1995 



LIB*. 




United States Department of the Interior/ National Park Service 



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Printed on Recycled Paper 



Report on Effects of Aircraft Overflights 
on the National Park System 

July 1995 



United States Department of the Interior/ National Park Service 
Prepared Pursuant to Public Law 100-91, The National Park Service Overflights Act of 1987 



Digitized by the Internet Archive 

in 2012 with funding from 

LYRASIS Members and Sloan Foundation 



http://www.archive.org/details/reportoneffectsoOOnati 



The Eloquent Sounds of Silence 



Everyone of us knows the sensation of going up, on retreat, to a high place and feeling ourselves so lifted up that 
we can hardly imagine the circumstances of our usual lives, or all the things that make us fret. In such a place, in 
such a state, we start to recite the standard litany: that silence is sunshine, where company is clouds; that silence 
is rapture, where company is doubt; that silence is golden, where company is brass. 

But silence is not so easily won. And before we race off to go prospecting in those hills, we might usefully recall 
that fool's gold is much more common and that gold has to be panned for, dug out from other substances. "All 
profound things and emotions of things are preceded and attended by Silence," wrote Herman Melville, one of 
the loftiest and most eloquent of souls. Working himself up to an ever more thunderous cry of affirmation, he 
went on. "Silence is the general consecration of the universe. Silence is the invisible laying on of the Divine 
Pontiff's hands upon the world. Silence is the only Voice of our God. " For Melville, though, silence finally meant 
darkness and hopelessness and self-annihilation. Devastated by the silence that greeted his heartfelt novels, he 
retired into a public silence from which he did not emerge for more than 30 years. Then, just before his death, he 
came forth with his final utterance — the luminous tale of Billy Budd — and showed that silence is only as worthy as 
what we can bring back from it. 

We hove to eorn silence, then, to work for it: to make it not an absence but a presence; not emptiness but 
repletion. Silence is something more than just a pause; it is that enchanted place where space is cleared and time 
is stayed and the horizon itself expands. In silence, we often say, we can hear ourselves think; but what is truer to 
say is that in silence we can hear ourselves not think, and so sink below our selves into a place far deeper than 
mere thought allows. In silence, we might better say, we can hear someone else think. 

Or simply breathe. For silence is responsiveness, and in silence we can listen to something behind the clamor of 
the world. "A man who loves God, necessarily loves silence," wrote Thomas Merton, who was, as a Trappist, a 
connoisseur, a caretaker of silences. It is no coincidence that places of worship are places of silence; if idleness is 
the devil's playground, silence may be the angels'. It is no surprise that silence is an anagram of license. And it is 
only right that Quakers all but worship silence, for it is the place where everyone finds his God, however he may 
express it. Silence is an ecumenical state, beyond the doctrines and divisions created by the mind. If everyone has 
a spiritual story to tell of his life, everyone has a spiritual silence to preserve. 



in 



So if is that we might almost say silence is the tribute we pay to holiness; we slip off words when we enter a 
sacred space, just as we slip off shoes. A "moment of silence" is the highest honor we can pay someone; i* is the 
point at which the mind stops and something else takes over (words run out when feelings rush in). A "vow of 
silence" is for holy men the highest devotional act. We hold our breath, we hold our words; we suspend our 
chattering selves and let ourselves "fall silent, " and fall into the highest place of all. 

It often seems that the world is getting noisier these days: in Japan, which may be a model of our future, cars and 
buses have voices, doors and elevators speak. The answering machine talks to us, and for us, somewhere above 
the din of the TV; the Walkman preserves a public silence but ensures that we need never — in the bathtub, on a 
mountaintop, even at our desks — be without the c/ongor of the world. White noise becomes the aural equivalent 
of the clash of images, the nonstop blast of fragments that increasingly agitates our minds. As Ben Okri, the 
young Nigerian novelist, puts it, "When chaos is the god of an era, clamorous music is the deity's chief 
instrument." 

There is, of course, a place for noise, as there is for daily lives. There is a place for roaring, for the shouting 
exultation of a baseball game, for hymns and spoken prayers, for orchestras and cries of pleasure. Silence, like 
all the best things, is best appreciated in its absence: if noise is the signature tune of the world, silence is the 
music of the other world, the closest thing we know to the harmony of the spheres. But the greatest charm of 
noise is when it ceases. In silence, suddenly, it seems as if all the windows of the world are thrown open and 
everything is as clear as on a morning after the rain. Silence, ideally hums. It charges the air. In Tibet, where the 
silence has a tragic cause, it is still quickened by the fluttering of prayer flag, the tolling of temple bells, the roar 
of wind across fhe plains, the memory of chant. 

Silence, then, could be said to be the ultimate province of trust: it is the place where we trust ourselves to be 
alone; where we trust others to understand the things we do not say; where we trust a higher harmony to assert 
itself. We all know how treacherous are words, and how often we use them to paper over embarrassment, or 
emptiness, or fear of the larger spaces that silence brings. "Words, words, words" commit us to positions we do 
not really hold, the imperatives of chatter; words are what we use for lies, false promises and gossip. We babble 
with strangers; with intimates we can be silent. We "make conversation" when we are alone, or with those so 
close to us that we can afford to be alone with them. 

In love, we are speechless; in awe, we say, words fail us. 

— Pico Iyer 
Copyright 1 993 Time Inc. Reprinted with permission. 



IV 




United States Department of the Interior 

OFFICE OF THE SECRETARY 
WASHINGTON, D.C. 20240 



Honorable J. Bennett Johnston t p \ 1 VS** 

Chairman, Committee on Energy ot-» 

and Natural Resources 
United States Senate 
Washington, D.C. 20510 

Dear Mr. Chairman: 

Pursuant to the provisions of the National Park Overflights Act of 
1987, Public Law 100-91, the Department of the Interior is pleased 
to submit the study report on the impacts of aircraft flights over 
units of the National Park system. 

The study identifies the problems associated with aircraft flights 
over units of the National Park System, and distinguishes between 
the impacts caused by sightseeing aircraft, military aircraft, 
commercial aviation, general aviation, and other forms of aviation 
which affect these units. The study also identifies those National 
Park System units in which the most serious adverse impacts from 
aircraft overflights exist, and pursuant to the Overflights Act, 
reports particular overflight problems at five units of the System. 
The report also includes recommendations from the National Park 
Service to provide for "substantial restoration of the natural 
quiet and experience" for Grand Canyon National Park. 

An identical letter is being sent to the Honorable Malcolm Wallop, 
Ranking Minority Member, Committee on Energy and Natural Resources, 
United States Senate, the Honorable George Miller, Chairman, 
Committee on Natural Resources, United States House of 
Representatives, the Honorable Don Young, Ranking Minority Member, 
Committee on Natural Resources, United States House of 
Representatives, and the Honorable William F. dinger, Ranking 
Minority Member, Committee on Public Works and Transportation, 
Subcommittee on Aviation, United States House of Representatives. 

Sincerely, 



George T. [Frampton, Jr.jf 
Assistant Secretary for Fish 
and Wildlife and Parks 



Enclosure 




United States Department of the Interior 

OFFICE OF THE SECRETARY 
WASHINGTON, D.C. 20240 

Honorable George Miller 

Chairman, Committee on Natural . n V$\ 

Resources C^p A *■ 

U.S. House of Representatives 
Washington, D.C. 20515 

Dear Mr. Chairman: 

Pursuant to the provisions of the National Park Overflights Act 
of 1987, Public Law 100-91, the Department of the Interior is 
pleased to submit the study report on the impacts of aircraft 
flights over units of the National Park system. 

The study identifies the problems associated with aircraft 
flights over units of the National Park System, and distinguishes 
between the impacts caused by sightseeing aircraft, military 
aircraft, commercial aviation, general aviation, and other forms 
of aviation which affect these units. The study also identifies 
those National Park System units in which the most serious 
adverse impacts from aircraft overflights exist, and pursuant to 
the Overflights Act, reports particular overflight problems at 
five units of the System. The report also includes 
recommendations from the National Park Service to provide for 
"substantial restoration of the natural quiet and experience" for 
Grand Canyon National Park. 

An identical letter is being sent to the Honorable J. Bennett 
Johnston, Chairman, Committee on Energy and Natural Resources, 
United States Senate, the Honorable Malcolm Wallop, Ranking 
Minority Member, Committee on Energy and Natural Resources, 
United States Senate, the Honorable Don Young, Ranking Minority 
Member, Committee on Natural Resources, United States House of 
Representatives, and the Honorable William F. dinger, Ranking 
Minority Member, Committee on Public Works and Transportation, 
Subcommittee on Aviation, United States House of Representatives. 



Sincerely, 



Cs?e. 




George TJ Frampton, Jr. 
Assistant Secretary for Fish 
and Wildlife and Parks 
Enclosure 



fr 



VI 



© 



800 Independence Ave.. S.W 
LLS Department Washington, DC 20591 

ot Transportation 

Federal Aviation 
Administration 

OCT 2 | 094 

Mr. John J. Reynolds 
Deputy Director 
National Park Service 
P.O. Box 37127 
Washington, DC 20013-7127 

Dear Mr. Reynolds: 

The Department .: f Transportation (DOT) has reviewed the final report that the 
National Park Service (NPS) has prepared and submitted to Congress pursuant to 
Public Law (P.L.) 100-91. We appreciate the opportunity the NPS provided for us to 
review the report in draft form and the responsiveness of the NPS to our comments and 
concerns. 

The Department of the Interior (DOI) and DOT have made great strides recently in 
limiting the impacts of aircraft noise on national parks while allowing aviation vitality 
to continue. The efforts of the DOT/DOI Interagency Working Group established last 
December by Secretary Pena and Secretary Babbitt have resulted in a productive new 
working relationship for resolving issues effectively in the Grand Canyon and other 
units of the National Park System. I believe the group embodies the spirit of the 
Clinton Administration's effort to reinvent government. Therefore, I commend the 
report's strong support of continuing the Interagency Working Group's efforts and 
concur with your recommendation to identify and document a process for addressing 
these issues at local levels. The Interagency Working Group would be the appropriate 
mechanism for establishing a memorandum of understanding defining the scope of our 
collective efforts and the procedures for surfacing and resolving these concerns. 

While we reached an understanding on most issues in the NPS report, a number of 
unresolved DOT concerns remain. This letter identifies the major unresolved issues 
and renews our commitment to finding workable solutions. 

First, the appropriate metric for assessing noise impacts and standard for determining 
appropriate corrective actions remains a primary issue. Environmental actions must be 
based on objective measures that are capable of withstanding both legal and technical 
challenges. The report continues to recommend percent of time audible, or audibility, 
as the trigger for further action. We do not object to the NPS's use of audibility as a 
determinant for further noise analysis using equivalent sound level (L^) or another 
scientifically validated metric. However, audibility should not be used to determine the 



VII 



need for Federal actions to mitigate aircraft noise in parks without the benefit of 
additional analysis. Considerably more work needs to be done to validate both the 
NPS survey results and the derivative dose-response relationships before this 
methodology is used as a basis for making decisions that will affect aviation. The DOT 
supports your efforts to refine existing noise methodologies for assessing aviation noise 
impacts on parks. We will continue to work with you in achieving this goal. 

Second, the issues of defining natural quiet, the extent to which a natural quiet standard 
should be applied to units of the National Park System, and what constitutes its 
substantial restoration are significant for both the NPS and the Federal Aviation 
Administration (FAA). The DOT recognizes the NPS's mandate for substantially 
restoring natural quiet in the Grand Canyon and understands NPS's interest in 
achieving this goal at other units of the National Park System. However, we question 
the practicability of applying this standard throughout the National Park System, 
particularly when coupled with use of the audibility measure as a trigger for action. 
A standard of "natural quiet" could likely be achieved only by the virtual elimination of 
all overflights. We believe that it would establish an unrealistically high goal, one that 
may only lead to future frustration for all concerned. Although the Congress did not 
request the NPS to study other types of noise, we think the report needs to be read and 
evaluated with the understanding that there are multiple sources of noise impacting 
national parks as confirmed by visitor surveys. While the NPS studies confirm that 
aviation noise impacts a limited number of parks and perhaps only a limited number of 
sites within those parks, at other parks there is no problem associated with aircraft 
sounds. We will be pleased to continue working with you in developing a viable 
understanding of the relationship between natural quiet and feasible levels to be 
obtained from mitigating aviation noise impacts. 

Third, the DOT supports P.L. 100-91's objective of substantially restoring natural 
quiet in the Grand Canyon. The NPS report defines such substantial restoration to 
mean "that 50 percent or more of the park achievefsl 'natural quiet' (i.e.. no aircraft 
audible;) for 75-100 percent of the day. " (Emphasis in original.) The FAA is 
conducting an operational and noise analysis of the report's Grand Canyon 
recommendations to identify their potential impact on overflights, effectiveness in 
reducing noise levels, and feasibility for implementation. We will evaluate the impact 
of high altitude overflights on natural quiet, any potential change in the noise 
environment should the flight-free zone ceilings be raised, and the impacts on both 
noise and aviation of each of the report's recommendations for changing current 
SFAR 50-2 provisions regarding flight corridors and routes. Our evaluation will 
include not only the noise reductions which would be achieved but also the safety and 
other relevant impacts. 



VIII 



Fourth, the FAA has sole statutory authority for the control of airspace use and the 
DOT is committed through the Interagency Working Group effort to resolving aviation 
noise issues in parks. For safety and other reasons, this authority should and, we 
assume, will remain exclusively with the FAA. Accordingly, we would fmd 
inconsistent with these statutory responsibilities any suggestion in the report that the 
NPS could act to direct airspace actions through issuance of concession permits or 
other mechanisms. The DOT recognizes that the NPS has significant park management 
concerns that, in some cases, may support action by the FAA to adjust or restrict 
aviation. However, any changes in aviation must be assessed in the context of the 
national airspace system, with safety as a paramount factor and the public interest in air 
commerce as a significant consideration. 

It is the policy of the Federal Government that the FAA, like other agencies, will 
exercise its authority in a manner that will enhance the environment, and that the FAA 
will make a special effort - insofar as is technologically and economically practicable - 
to preserve the natural beauty of public park and recreation lands, wilderness areas, 
and wildlife refuges. The DOT supports your proposal for establishing a management 
process that will facilitate identification, coordination, and resolution of aviation issues 
in parks. The actions and commitment of both of our departments through the 
Interagency Working Group demonstrate that this process is well under way. 
Continuing these efforts will assure that we find a balance between preservation of park 
values by the NPS and the FAA's responsibility to assure the safety and efficiency of 
aviation. 

I reiterate that we are committed to working with you to address the issues raised in the 
report. As you know, the FAA already has undertaken a number of non-regulatory 
initiatives to address noise and safety concerns at the Statue of Liberty, Glacier 
National Park, Zion National Park, and Hawaii Volcanoes National Park. We are 
ready to proceed with similar initiatives at Perry's Victory and International Peace 
Memorial and at the Mt. Rushmore National Memorial within the next six months. We 
will schedule an Interagency Working Group meeting specifically to develop an action 
plan for an orderly prioritized approach to the recommendations in your report. 

The DOT will be pleased to continue working with you in resolving these and other 
aviation issues affecting the National Park System. 

Sincerely, 



A 




- Barry L. Valentine 
Assistant Administrator for Policy, Planning, 
and International Aviation 



CONTENTS 



EXECUTIVE SUMMARY 

1 INTRODUCTION 3 

2 ANSWERS TO QUESTIONS 5 

2.1 Nature and Scope of the Overflight Problem 5 

2.1.1 Number of Parks Affected 5 

2.1.2 Types of Aircraft 5 

2.1.3 Aircraft Sound Levels 6 

2.1.4 Relative Seriousness of Overflight Problem 6 

2.2 Other Injurious Effects of Overflights on Resources 7 

2.2.1 Impacts on Cultural and Historical Resources, Sacred Sites and Ceremonies 7 

2.2.2 Impacts on Wildlife 8 

2.2.3 Impacts on Natural Quiet - 9 

2.3 Proper Minimum Altitude 11 

2.4 Effects of Minimum Altitudes Established Over Yosemite and Haleakala National Parks .... 12 

2.5 Has the Plan for Airspace Above the Grand Canyon Substantially Restored Natural Quiet? ... 12 

2.6 Revisions in the Grand Canyon Airspace Management Plan 13 

2.7 Impairment of Visitor Enjoyment 16 

2.7.1 Background 16 

2.7.2 Impacts Across the National Park System 16 

2.7.3 Impacts at Specific Parks 19 

2.7.4 Impacts at Specific Sites 20 

2.7.5 Identification, Analysis and Mitigation of Impacts 22 

2.8 Impacts on Safety 24 

2.9 Values Associated with Overflights 24 



XI 



CONTENTS 



3 Conclusions 25 

4 Recommendations 27 

4.1 Recommendation 1 27 

4.2 Recommendation 2 28 

4.3 Recommendation 3 28 

4.4 Recommendation 4 30 

FAA to Address High Priority NPS Airspace/Park Use Issues 30 

4.4.1 NPS Managerial Priorities 30 

4.4.2 NPS Priorities for Protection of Natural Quiet 31 

4.4.3 NPS Priorities for Resolution of Safety Concerns 31 

4.4.4 NPS Priorities for Problem Solving with Department of Defense 32 

4.5 Recommendation 5 33 

4.6 Recommendation 6 33 

4.7 Recommendation 7 35 

4.8 Recommendation 8 ' 35 

4.9 Recommendation 9 36 

4.10 Recommendation 10 36 

Epilogue 36 



REPORT TO CONGRESS 

CHAPTER 1: INTRODUCTION 39 

1.1 Background 39 

1.2 Public Law 100-91 and this Report 42 

1.3 Organization of Report 43 

1.3.1 The Nature and Scope of Overflight Problems 43 

1.3.2 Effects of Overflights on Natural Quiet 44 

1.3.3 Effects on Cultural and Historical Resources, Sacred Sites and Ceremonies 44 

1.3.4 Effects on Wildlife 44 

1.3.5 Effects of Overflights on Visitors 44 

1.3.6 Aircraft Overflights and Safety 45 

1.3.7 Values Associated with Aircraft Overflights 45 

1.3.8 Restoration of Natural Quiet . . 45 

1.3.9 Conclusions, Issues and Recommendations 45 

1.3.10 Availability of NPS Studies 45 

CHAPTER 2: NATURE AND SCOPE OF OVERFLIGHT PROBLEMS IN THE NATIONAL PARK SYSTEM 47 
2 . 1 Survey of Park Managers , 49 

2.1.1 Number of Parks Affected 49 

2.1.2 Types of Aircraft Overflights 50 

2.1.3 Types of Impacts 50 

2.1.4 Estimated Numbers of Overflights 52 



XII 



Contenfs 



2.1.5 Superintendents' Judgments of Overflight Problems 55 

2.2 Estimates of Overflight Exposure 58 

2.3 Sound Measurement Results 60 

2.4 Summary 70 

CHAPTER 3: EFFECTS OF OVERFLIGHTS ON NATURAL QUIET 71 

3.1 How Important is Natural Quiet? 71 

3.1.1 Importance to the Congress 72 

3.1.2 Importance of Natural Quiet to the National Park Service 73 

3.1.3 Importance of Natural Quiet to Park Managers 75 

3.1.4 Importance of Natural Quiet to Park Visitors 77 

3.2 What is Natural Quiet? 78 

3.2.1 Qualitative Assessment of Natural Quiet 78 

3.2.2 Quantitative Assessment of Natural Quiet 79 

3.3 What Are the Characteristics of Natural Quiet? 80 

3.4 Why is it Difficult to Preserve Natural Quiet? 83 

3.5 Aircraft Overflight Effects on Natural Quiet 84 

3.6 Summary 85 

CHAPTER 4: EFFECTS ON CULTURAL AND HISTORIC RESOURCES, SACRED SITES, AND 

CEREMONIES 87 

4.1 Extent of Concern by Park Management and Visitors 89 

4.1.1 Park Management Assessment 89 

4. 1 .2 Visitor Assessment 91 

4.2 Acoustic Impact on Cultural and Historical Resources 92 

4.3 Vibration Impact on Cultural and Historical Resources 95 

4.3.1 How Structures Respond 96 

4.3.2 Types of Aircraft Noise That Can Excite Structural Response 97 

4.3.3 Damage Potential 99 

4.3.4 Mitigation 101 

4.4 Summary 102 

CHAPTER 5: EFFECTS OF OVERFLIGHTS ON WILDLIFE 103 

5.1 Introduction 103 

5.2 Physiological Responses to Aircraft Overflights , . . . 105 

5.3 Behavioral Responses to Aircraft Overflights 106 

5.4 Indirect Effects of Disturbance from Overflights, and Consequences for Animals 107 

5.4.1 Accidental Injury 113 

5.4.2 Reproductive Losses 114 

5.4.3 Energy Losses 116 

5.4.4 Habitat Avoidance and Abandonment 117 

5.4.5 Potential Bird Strike Hazards 118 

5.5 Factors that Influence Animal Responses to Aircraft 119 

5.5.1 How Animals Perceive the Aircraft Stimulus 119 

5.5.2 Aircraft Sound and Animal Hearing 120 



XIII 



CONTENTS 



5.5.3 Increased Tolerance to Overflights 121 

5.6 Biotic Factors that Influence Animal Responses to Aircraft 122 

5.7 Problems with Detecting Long-Term Effects of Aircraft Disturbance 124 

5.8 Overflight Impacts on Endangered Species 125 

5.9 Overflight Impacts on National Park Animals 126 

5.10 Development of Impact Criteria 127 

5.1 1 Summary 130 

CHAPTER 6: EFFECTS OF OVERFLIGHTS ON VISITOR ENJOYMENT 131 

6.1 Introduction 131 

6.2 The System-Wide Impacts of Overflights on Visitors 133 

6.2.1 Importance of Natural Quiet 134 

6.2.2 Impacts Produced by Hearing and Seeing Aircraft 134 

6.2.3 Impacts Among Different User Groups Produced by Hearing Aircraft 136 

6.3 Impacts at Specific Parks and at Specific Sites 137 

6.3.1 Impacts at Specific Parks 138 

6.3.2 Impacts at Specific Sites " 143 

6.4 Identification, Analysis and Mitigation of Impacts 147 

6.4.1 Identification 147 

6.4.2 Analysis and Mitigation 149 

6.4.3 Limitations 151 

6.5 Summary 152 

CHAPTER 7: AIRCRAFT OVERFLIGHTS AND SAFETY 155 

7.1 Concerns of Park Management 155 

7.2 Concerns of Park Visitors 159 

7.3 Outdoor Recreation Community Concerns 161 

7.4 Temporary Flight Restriction (TFR) Problems 162 

7.5 Summary 163 

CHAPTER 8: VALUES ASSOCIATED WITH AIRCRAFT OVERFLIGHTS 165 

8.1 Values Associated with Administrative Use of Aircraft 165 

8.2 Values Associated with Aerial Tourism 168 

8.2.1 Tour Passenger Survey Results 168 

8.2.2 Are Air Tour Passengers Park Visitors? 175 

8.3 Value of Overflights to Local Economies 177 

8.4 Values and Impacts of Aerial Filming 177 

8.5 Summary . . 178 

CHAPTER 9: RESTORATION OF NATURAL QUIET 179 

9.1 Report on Section 2 Requirements — Yosemite and Haleakala National Parks 180 

9.1.1 Yosemite National Park 180 

9.1.2 Haleakala National Park 181 

9.2 Report on Section 3 Requirements: Grand Canyon National Park 181 

9.2.1 Defining a Substantial Restoration of Natural Quiet 182 

9.2.2 Special Federal Aviation Regulations 50-2 182 



XIV 



Contents 



9.2.3 Evaluation of Restoration Efforts (SFAR 50-2) 182 

9.2.4. Summary of Section 3 Requirements 195 

9.3 What are the Opportunities for Solutions? 198 

9.3.1 Realistic Expectations 198 

9.3.2 Realistic Opportunities 199 

9.3.3 Environment Needed for Effective Comprehensive Solutions 200 

9.4 Summary 202 

CHAPTER 10: CONCLUSIONS AND RECOMMENDATIONS 203 

10.1 Conclusions 203 

10.2 Airspace Management-Issues: The NPS Perspective 207 

10.2.1 The FAA and The NPS: Learning How to Work Together 208 

10.2.2 Military Airspace/Park Use Issues: Prospects for Change 209 

10.3 NPS Recommendations to Congress 212 

10.3.1 RECOMMENDATION 1 212 

10.3.2 RECOMMENDATION 2 212 

10.3.3 RECOMMENDATION 3 213 

10.3.4 RECOMMENDATION 4 215 

10.3.5 RECOMMENDATION 5 217 

10.3.6 RECOMMENDATION 6 218 

10.3.7 RECOMMENDATION 7 220 

10.3.8 RECOMMENDATION 8 220 

10.3.9 RECOMMENDATION 9 220 

10.3.10 RECOMMENDATION 10 221 

Epilogue 234 



APPENDIXES 

APPENDIX A: Studies Conducted in Response to P. L. 100-91 237 

APPENDIX B: 98 Parks Identified as Potentially Having Overflight Problems 241 

APPENDIX C: Legislative Proposals to Control Airspace Over National Park Lands 245 

APPENDIX D: Advanced Notice of Proposed Rulemaking Issued Joindy by 

Federal Aviation Administration and National Park Service . . , 297 

APPENDIX E: Policy on Overflights of Designated Wilderness and Wild and Scenic Rivers 305 

APPENDIX F: Interagency Airspace/Natural Resource Coordination Group (IANRCG) 309 

APPENDIX G: Deputy Under Secretary of Defense (Environmental Security) 313 

LIST OF REFERENCES 317 



xv 



CONTENTS 



LIST OF TABLES 

EXECUTIVE SUMMARY 

Table 1: Questions Posed by P. L. 100-91 4 

Table 2: Importance of Natural Quiet and Natural Scenery as Reasons for Park Visit 17 

Table 3: Numbers of Visitors Hearing or Seeing Aircraft, and the Resultant Impacts 18 

Table 4: Visitor Survey Parks with More than 10,000 Visitors Impacted by Overflights during Survey .... 20 

REPORT TO CONGRESS 

Table 1.1: Questions Posed by P. L. 100-91 43 

Table 2.1 : National Parks Whose Managers are Very to Extremely Concerned about Aircraft Overflights . . 56 

Table 5.1: General Responses by Specific Animal Species to Aircraft Overflights 108 

Table 6. 1 : Importance of Natural Quiet and Natural Scenery as Reasons for Park Visit 135 

Table 6.2: Numbers of Visitors who Reported Hearing or Seeing Aircraft 135 

Table 6.3: Impacts that Resulted from Hearing Aircraft 136 

Table 6.4: Annoyance that Resulted from Seeing Aircraft - 136 

Table 6.5: Reported Exposure and Impact from Hearing Aircraft at Visitor Survey Parks 139 

Table 6.6: Visitor Survey Parks with More than 10,000 Visitors Impacted by Overflights During Survey . . 141 

Table 6.7: Dose-Response Data Collection Study Areas 144 

Table 7.1: Parks Where Safety is Perceived as a Serious, or Very Serious Problem 157 

Table 7.2: Visitor Safety Concerns Reported to Park Management During FY 1992 158 

Table 9.1: Grand Canyon National Park Management Objectives 184 

Table 9.2: Percent of Time Aircraft were Audible 187 



LIST OF FIGURES 

EXECUTIVE SUMMARY 

Figure 1 : Impacts of Hearing Aircraft Among Different Visitor Groups 19 

Figure 2 : Numbers of Visitors Hearing Aircraft and Annoyed by Aircraft at Visitor Survey Parks 20 

Figure 3: Dose- Response Curve for Visitor Annoyance vs Percent of Time Aircraft are Heard 21 

Figure 4: Dose-Response Curve for Visitor Annoyance vs Hourly Equivalent Sound Level 21 

REPORT TO CONGRESS 

Figure 2.1: Extent of Aircraft Overflight Problems in the National Park System 49 

Figure 2.2: Locations of the 98 Park Units with Identified Aircraft Overflight Problems 50 

Figure 2.3: Types of Aircraft Overflying National Parks as Identified by Managers 51 

Figure 2.4: Park Manager Judgements of Types of Impacts Produced by Aircraft Overflights 51 

Figure 2.5: Reported Number of Overflights per Week by Aircraft Type for All Parks 52 

Figure 2.6: Reported Number of Overflights per Week Reduced by Four Parks 53 

Figure 2 .7 : Distribution of Overflights per Day for All Aircraft Combined 54 



Confenfj 



Figure 2.8: Distribution of Overflights per Day for Military Aircraft 54 

Figure 2.9: Distribution of Overflights per Day for Sightseeing Aircraft 54 

Figure 2.10: Distribution of Overflights per Day for Commercial Aircraft 55 

Figure 2.1 1: Distribution of Overflights per Day for General Aviation Aircraft 55 

Figure 2.12: Managers' Rating of Ten Potential Problems in Their Parks 57 

Figure 2.13: Managers' Rating of Sound-Related problems in Their Parks 57 

Figure 2.14: Managers' Reported Degree of Overall Concern about Overflights 58 

Figure 2.15: Managers' Rating of Most Bothersome Aspects of Overflights 59 

Figure 2.16: Managers' Rating of Overflight Impacts on Visitors' Enjoyment 59 

Figure 2.17: Sound Measurement Results Acquired in Eight National Parks 62 

Figure 2.18: Acoustic Profile Data from Grand Canyon National Park 66 

Figure 2.19: Acoustic Profile Data from Haleakala and Hawaii Volcanoes National Parks 68 

Figure 3.1: Importance to Management of Various Opportunities 76 

Figure 3.2: Management Perspective on Interference with Opportunities 76 

Figure 3.3: Management Reports of Aircraft Impact on Park Resources 77 

Figure 3.4: Grand Canyon Visitor Reports of Aircraft Impact on Park Resources 77 

Figure 3.5: Sound Level Ranges Between Park and Non-Park Settings 79 

Figure 3.6: Measured Ambient Sound Levels Along Colorado River in Grand Canyon National Park ... 81 

Figure 3.7: Measured Ambient Sound Levels Along the Canyon Rim in Grand Canyon National Park ... 81 

Figure 3.8: Measured Ambient Sound Levels in Hawaii Volcanoes and Grand Canyon National Park ... 81 

Figure 3.9: Protrusion of Aircraft Noise Above the Ambient in Various Settings 82 

Figure 4.1: Management Rating oflmportance of Providing Historical and Cultural Opportunities .... 90 

Figure 4.2: Management Perspective on Interference with Opportunities 90 

Figure 4.3: Visitor Ratings at Eight "Cultural" Parks of Aircraft Interferences with Historical 

and Cultural Significance of Park .' 91 

Figure 4.4: Percent of Visitors Reporting Interference with History or Culture at Specific Parks 92 

Figure 4.5: Representative Time History of a Sonic Boom "N-vvave" Pressure Pulse 97 

Figure 4.6: Helicopter "Blade Slap" Sound Wave Impinging on a Historical Site 99 

Figure 4.7: Helicopter "Thickness" Noise Radiating to a Cultural Resource 99 

Figure 5.1: Animal Responses to Low- Altitude Aircraft Overflights 123 

Figure 5.2: External Factors that Influence Animal Responses to Overflights 123 

Figure 6.1: Impacts of Hearing Aircraft Among Different Visitors Groups 137 

Figure 6.2: Percent of Visitors Hearing Aircraft and Annoyed by Aircraft at Visitor Survey Parks 140 

Figure 6.3: Percent of Visitors Hearing Aircraft and Annoyed by Aircraft at Five Specific Sites 140 

Figure 6.4 Numbers of Visitors Hearing Aircraft and Annoyed by Aircraft at Visitor Survey Parks .... 141 

Figure 6.5: Comparison of NPS Management Rankings with Percent of Visitors Hearing Aircraft 142 

Figure 6.6 Comparison of NPS Management Rankings with Percent of Visitors Annoyed 143 

Figure 6.7: Comparison of NPS Management Rankings with Number of Visitors Annoyed 143 

Figure 6.8: Dose-Response Curve for Visitor Annoyance vs Percent of Time Aircraft are Heard 145 

Figure 6.9: Dose- Response Curve for Visitor Annoyance vs Hourly Equivalent Sound Level 146 

Figure 6.10: Dose-Response Curves for Estimating Impacts at Sites Preserving Visitor Enjoyment .... 149 

Figure 6.1 1: Dose- Response Curves for Estimating Impacts at Sites Preserving Natural Quiet 149 

Figure 6.12: Dose- Response Curves for Analysis of Airspace at Sites Preserving Visitor Enjoyment .... 150 

Figure 7 . 1 : Manager Assessment of Visitor and Staff Safety 156 



XVII 



CONTENTS 



Figure 7.2: Perceptions Managers Have About Visitor and Staff Concerns for Safety 157 

Figure 7.3: Reported Aircraft Crashes in 91 NPS Units During the Past Five Years 160 

Figure 7.4: Visitor Assessment of Decreased Feelings of Safety Due to Aircraft Operations 160 

Figure 7.5: Visitor Assessment of Increased Feelings of Safety From Aircraft Overflights 161 

Figure 8.1: Most Prevalent Uses of Aircraft by NPS Park Management 166 

Figure 8.2: Annual Helicopter Flight Hours Flown by NPS Park Management 167 

Figure 8.3: Annual Fixed Wing Flight Hours Flown by NPS Park Management 167 

Figure 8.4: Relative Visitation Access Modes for Grand Canyon and Hawaiian Parks 168 

Figure 8.5: Passenger Reports of Air Tour Enjoyment 170 

Figure 8.6: Passenger Reports of Increased Appreciation of Park from Air Tours 170 

Figure 8.7: Passenger Willingness to Recommend Air Tours to Others 170 

Figure 8.8: Percentage of First Time Passengers on Air Tours . 171 

Figure 8.9: Passengers' Primary Reasons for Taking Air Tour 171 

Figure 8.10: Importance of Time Constraints as a Reason for Taking Air Tour 171 

Figure 8.1 1: Importance of Unique Perspective as a Reason for Taking Air Tour 172 

Figure 8.12: Importance of Health Limitations as a Reason for Taking Air Tour 172 

Figure 8.13: Passengers' Plans for Touring Park on the Ground as Well 173 

Figure 8.14: Passenger Reports of Importance of Air Tour to Overall Enjoyment of the Park 173 

Figure 8.15: Passenger Reports of Importance of Ground Tour to Overall Enjoyment of the Park .... 174 

Figure 8.16: Passengers' Assessment of Disruptive Impact of Air Tours to Ground Visitors 174 

Figure 8.17: Passengers' Assessment of Whether Air Tour Benefits Outweigh Impacts on the Ground . . 175 

Figure 9.1: Grand Canyon National Park Special Flight Rules Area 183 

Figure 9.2: Grand Canyon National Park Acoustic Monitoring Sites 186 

Figure 9.3: Visitor Reports of Reasons for Visiting the Canyon 190 

Figure 9.4: Visitor Reports of the Most Important Reasons 191 

Figure 9.5: Visitor Reports of Hearing Aircraft 192 

Figure 9.6: Visitor Reports of Impacts 192 

Figure 9.7: I nappropriateness of Overflights 193 

Figure 9.8: Visitor View of Park Overflight Policy 194 

Figure 9.9: Visitor Support for Overflight Limits . 195 

Figure 9.10: Computer Modeled Natural Quiet Restoration — 1989 Tour Operations 196 

Figure 9.1 1: Computer Modeled Natural Quiet Restoration — 2010 Tour Operations 197 

Figure 9.12: Observer-Based Audibility Contours Comparing Quiet and Other Aircraft 201 

Figure 10. 1 : Recommended Special Flight Rules Area: NPS Proposal for Flight Free Zones and Corridors . 224 
Figure 10.2: Substantial Restoration of Natural Quiet — Year 2010: The Result of the 

NPS Recommendation . 232 

Figure 10.3: Percent of GCNP in Natural Quiet (100%) if NPS Recommendation Adopted 233 

Figure 10.4: Percent of Park Where Natural Quiet Substantially Restored: A Comparison 

Between NPS Recommendation and No Action 233 



ACKNOWLEDGEMENTS 



This Report to Congress provides the U.S Department oflnterior, National Response to Public Law 100-91, the 
National Parks Overflights Act of 1987. The information presented herein represents the combined efforts of 
many scientists, specialists, and park managers and staff. In particular, the National Park Service would like to 
acknowledge the contribution of the following: 

The Department of Interior — Department of Transportation Interagency Working Group 

Ms. Jackie Lowey, Ms. Barbara West, Mr. Joseph Canny, Mr. John Reynolds, 
Mr. Dale McDaniel, Mr. Destry Jarvis, Mr. Hal Becker, and Dr. Wes Henry 

Grand Canyon National Park 

Superintendents Boyd Evison and Robert Arnberger and Staff, especially Mr. Mike Ebersole and Ms. Linda Mazzu. 

The National Park Service, Denver Service Center 

Mr. Rick Ernenwein and Mr. Elmer Hernandez 

Research Contractors and Subcontractors 

Harris Miller Miller & Hanson Inc: Mr. Nicholas P. Miller and Staff 
BBN Systems and Technologies: Dr. Sanford Fidell and Staff 
HBRS, Inc.: Dr. Robert Baumgartner and Dr. Cary McDonald 
Sterna Fuscata, Inc.: Mr. Douglas Gladwin and Ms. Alexie McKechnie 
Research Triangle Institute: Dr. Ronaldo Iachan 



XIX 



£k&t#i$y& 




or* 





EXECUTIVE SUMMARY 

Report on Effects of Aircraft Overflights 

on the National Park System 

1 Introduction 

The National Park Service (NPS) was created by Congress to 

". . . promote and regulate the use of Federal areas known as 
national parks . . . [so as to] conserve the scenery and the 
natural and historic objects and the wild life therein and to 
provide for the enjoyment of the same in such manner and by 
such means as will leave them unimpaired for the enjoyment of 
future generations." 

In doing so, the NPS mission was defined as two-fold: conservation of 
resources and providing for visitor enjoyment. But the NPS Organic Act was 
amended by the Redwoods Act of 1978, and this act unambiguously defines 
resource preservation as the primary responsibility for the National Park 
Service. Given that natural quiet is a clearly identified resource, that aircraft 
overflights can affect this resource and that the FAA controls use of the 
airspace, meshing the disparate missions of the NPS and FAA has, until 
recendy, appeared to be an intractable task. 



NPS organic act, 1 6 USC 1 



EXECUTIVE SUMMARY: Introduction 



The NPS manages the many units of the National Park System to accomplish 
the overall goals of the Organic Act and any specific goals identified when 
Congress established the various parks, monuments, preserves, recreation 
areas, and other units. Among the goals are provision of opportunities for 
visitors, such as the opportunity to experience solitude or to experience 
nature in a state unaffected by the effects of civilization. Increased numbers 
of low-flying aircraft over various units of the National Park System diminish 
opportunities for solitude and natural quiet, and raise concerns about other 
impacts and the appropriateness of this activity over national parks. To these 
ends, in August of 1987 Congress passed Public Law 100-91, the National 
Parks Overflights Act. The Act directed the Secretary of the Interior to 
conduct studies that provide information and evaluations regarding nine 
questions relevant to national parks. Table 1 lists the specific questions to be 

answered, identifies the section of the law which poses each question and the 

2 
chapter(s) of the full report which provides the answers . 



TABLE 1: QUESTIONS POSED BY P.L. 100-91 


Question to be Answered 


Section of P.L. 

100-91 where 

Question is Posed 


Chapters of Report 

that Address the 

Question 


1 . What is the nature and scope of the overflight problem in the National Park 
System? 


§1 (b) 


2 


2. What are other injurious effects of overflights on the natural, historical, and 
cultural resources for which such units were established? 


§ 1(c)(3) 


3,4,5 


3. a. What is the proper minimum altitude which should be maintained by 
aircraft when flying over units of the National Park System? 

3b. What have been the effects of the minimum altitudes established over 
Yosemite and Haleakala National Parks? 

3c. Has the plan for management of airspace above the Grand Canyon 
succeeded in substantially restoring the natural quiet in the park? 

3d. What revisions in the airspace management plan for the Grand Canyon 
may be of interest? 


§1 (a) 

§2.(c) 
§3.(b)(3)(A) 
§3.(b)(3)(B) 


3 
9 
9 
10 


4. What is the impairment of visitor enjoyment associated with flights over 
such units of the National Park System? 


§1 (c)(2) 


6 


5. What are the impacts of aircraft noise on the safety of the park system 
users, including hikers, rock-climbers, and boaters? 


§1 (c)(1) 


7 


6. What are the values associated with aircraft flights over such units of the 
National Park System in terms of visitor enjoyment, the protection of persons 
or property, search and rescue operations and firefighting? 


§1 (c)(4) 


8 



2. The law specifically excludes from consideration all National Park System units in the State of Alaska. So all information in this report, when applicable 
to the "park system " really applies to the non-Alaskan units of the National Park System. This distinction is repeated where appropriate. 



2. 1 Nature and Scope of the Overflight Problem 



2 Answers to Questions 

In response to these questions, the NPS conducted numerous studies, all of 
which are listed in Appendix A of this report. The many studies provide 
answers to the questions posed by the National Parks Overflight Act. This 
section summarizes the answers and refers to the chapters that present the 
supporting information. 

2. 1 Nature and Scope of the Overflight Problem 

2.1.1 Number of Parks Affected 

Aircraft overflights can and do produce impacts both on park resources and 
on visitors. These impacts, however, do not occur evenly throughout the 
National Park System, but occur at some parks to a considerably greater 
extent than at others depending upon local air traffic (§2.1 .4 ), and local 
park management objectives (§2.1.5). Congruence between management 
perceptions and visitor responses (§6.3.1) means it is likely that as many as 
50 to 100 units of the park system currendy may have overflight problems in 
need of resolution (§2.1 .1), and that 30-40 of these parks are priorities for 
research and problem solving. Passenger satisfaction with air tours (§8.2. 1) 
and park visitor interest in seeing parks from the air imply that the demand 
for air tours will continue and the NPS expects further increases in the 
number of tour overflights and in the number of park units affected by air 
tours. 

2.1.2 Types of Aircraft 

Reported numbers of overflights by type of operation vary considerably from 
park to park, with slightly less than half the parks reporting more than 10 
overflights per day. Commercial passenger aircraft, sightseeing and general 
aviation operations are more prevalent than other types of overflights. 
Military overflights and park administrative overflights are the least common 
(§2.1.4). 

For the parks where commercial passenger aircraft overflights occur, these 
aircraft tend to produce the highest numbers of overflights; sightseeing or 
general aviation aircraft, on average, produce about one-sixth as many 
overflights as commercial passenger planes. Military aircraft average about 
half as many overflights as sightseeing or general aviation aircraft. Overflights 
for NPS administrative and emergency purposes are insignificant in numbers 
(§2.1.4). 



Refers to specific chapter section where supporting information appears. 



EXECUTIVE SUMMARY: Answers to Questions 



2.1.3 Aircraft Sound Levels 

Sound levels were measured at various locations in eight national parks . 
though decibel levels were collected, data were also collected on how long 
aircraft could be heard. During measurement periods that generally included 
several hours of data collection, aircraft could be heard from a low of about 5 
percent of the measurement time to highs of 70 to 90 percent of the time. 
Of 78 locations measured, aircraft were audible more than 50 percent of the 
time at 34 locations. The locations were not chosen randomly, so general 
judgements about the audibility of aircraft should not be made. However, 
these measurements show that in these parks, aircraft have a significant effect 
on the audible environment at some locations (§2.3). 

Decibel data show that non-aircraft background sound levels in parks can be 
exceedingly quiet, often less than 20 decibels more than half the time, and 
that aircraft levels can protrude well above these background sounds (§2.3). 
Flight- free zones and minimum altitudes can limit such protrusion, but 
ground elevations and distances to aircraft flights must be carefully 
considered. 

2.1.4 Relative Seriousness of Overflight Problem 

For parks affected by overflights, about 70 percent of the managers identified 
aircraft as a potential sound problem, while road traffic was identified as a 
potential problem by about 40 percent of these managers. Dess than 1 5 
percent of the managers identified each of four other sources (power 
generators, audio equipment, domestic animals, people talking) as potential 
sound problems (§2.1.5). 

Most, though not all, managers of the parks with perceived overflight 
problems rate aircraft as one of their more important management 
problems. Also, managers demonstrate differing degrees of concern about 
overflights. Hence any systematic method for assessing aircraft overflight 
problems should be designed to incorporate local management objectives in 
the identification of the problem and in developing solutions. The starting 
point for resolving overflight issues over national parks needs to begin with 
an examination of those parks whose managers are very to extremely 
concerned about overflights. 

Visitors' differing perceptions of overflight problems are discussed in 
section 2.7. 



4. Grand Canyon N.P., Haleakala N.P., Hawaii Volcanoes N.P., Cumberland Island N.S., Mount Rushmore N.M., Yosemile N.P., Pelroglyphs N.M. 
and Glacier N. P. 



2.2 Other Injurious Effects of Overflights on Resources 



2.2 Other Injurious Effects of Overflights on Resources 

Aircraft overflights appear to have adverse effects or impacts on other park 
resources, and studies examined the potential effects on cultural and 
historical resources, sacred sites and ceremonies, wildlife, and natural quiet. 

2.2. / Impacts on Cultural and Historical Resources, Sacred Sites and 
Ceremonies 

Park Manager and Visitor Opinions 

The park manager and visitor surveys provide two perspectives on the 
interference overflights may have on visitor's opportunity to appreciate the 
historical and/or cultural significance of the parks. About half of the 
approximately 1 00 park managers surveyed thought that aircraft activity 
interfered moderately, very much or extremely with the opportunity for 
visitors to appreciate these historical/cultural resources (§4.1.1). Based on 
the visitor survey, it is concluded that across the system, an estimated 4-5 
million visitors feel their opportunities to experience the historical and 
cultural resources in parks is impacted — a small percentage of the visitor 
population. 

Acoustic Impacts 

The sound from aircraft activity can impinge on the solemnity of sacred sites 
as well as interfere with Native American and other traditional ceremonies. 
As shown in Chapter 3, and discussed below under Impacts on Natural 
Quiet, national parks provide opportunities for quiet generally unavailable in 
common non-park settings. Quiet park surroundings can provide unique 
opportunities for visitors to experience cultural and historic sites and for 
traditional ceremonies to be conducted in an historically accurate audible 
environment — the environment that existed before the introduction of 
mechanized power. If national parks are to provide opportunities for visitors 
to see and experience authentic historical settings, for practitioners to 
conduct authentic ceremonies, and for visitors to witness such ceremonies, 
the parks must be able to control or limit the audible and visual intrusion of 
aircraft. Such intrusions not only detract from the authenticity of the 
experience, but for some settings and ceremonies, participants may consider 
intrusions to damage or destroy the very purpose of the setting or ceremony 
(§4-2). 

Induced Vibration Impacts 

The sound from aircraft activity can cause archeological resources, 
structures, and museum objects to vibrate. Depending on the character of 
the sound, the effects range from audible ratde, to items "walking" across 



EXECUTIVE SUMMARY: Answers to Questions 



surfaces, to fatigue cracking, and potentially to direct or indirect structural 
damage. Potential for impact depends upon the relationship of the aircraft 
overflight to the resource, the frequency of overflight, and the 
frequency-dependent responses of the resource to impinging sound waves. 
Some studies suggest that historic structures exposed either to sonic booms 
or to helicopter operations at close range may be at risk of weakening or 
being damaged. Situations need to be examined on a case-by-case basis. The 
NPS proposes, where warranted, to develop a systematic approach for 
examining appropriate structures to determine levels of sound-induced 
vibration. Lacking such detailed information, eliminating sonic booms or 
keeping helicopters distant should protect most structures (§4.3.2, §4.3.3, 
§4.3.4). 

2.2.2 Impacts on Wildlife 

The effects of overflights on wildlife are less well understood than are the 
effects of overflights on structures. Though there are many reports of 
behavioral responses in animals, these responses vary study to study, species 
to species, season to season, habitat to habitat (§5.3). Indirect effects on 
wildlife such as accidental injury, energy losses, habitat avoidance and 
abandonment are very difficult to detect, but some experts suspect that they 
occur (§5.4). Such uncertainties, however, do not prevent definition of 
impact criteria to use in judging potential for impacts on wildlife at specific 
parks. In the following criteria, "species of concern" include federally- or 
state-listed threatened, endangered, and candidate species, species of local 
economic importance, or species of particular concern to conservation or 
other interest groups. This definition can be expanded to include any species 
that is known to be susceptible to disturbance. "Habitat" is used to refer to 
the physical landscape and its ecosystem components that are subjected to 
overflights (§5. 10). The following guidelines can be used to identify impacts 
of overflights on wildlife. 

Negligible impacts 

■ No species of concern are present and either no or only minor 
impacts on any species are expected. 

■ Minor impacts that do occur have no secondary (long-term or 
population) effects. 

Low impacts 

■ Non-breeding animals of concern are present in low numbers. 

■ Habitat is not critical for survival and not limited to the area ot 
overflight use; other habitat meeting the requirements of animals of 
concern is found nearby and is already used by those species. 



2.2 Other Injurious Effects of Overflights on Resources 



■ Occasional fright responses are expected, but without apparent 
interference with feeding, reproduction, or other activities necessary 
for survival. 

■ No serious concerns are expressed by state or federal fish and 
wildlife officials. 

Moderate impacts 

■ Breeding animals of concern are present, and/or animals are present 
during particularly vulnerable life-stages such as migration or winter 
(depends upon the species in question). 

■ Mortality or interference with activities necessary to survival are 
expected on an occasional basis. 

■ Mortality and interference are not expected to threaten the 
continued existence of the species in the area. 

■ State and federal officials express some concern. 
High impacts 

■ Breeding individuals are present in relatively high numbers, and/or 
animals are present during particularly vulnerable life-stages. 

■ Habitat targeted for overflights has a history of use by the species 
during critical periods, and this habitat is not extensive outside the 
area targeted for overflight use; animals cannot go elsewhere to avoid 
impacts (animals can rarely "relocate" except temporarily). 

■ Mortality or other effects (injury, physiological stress, effects on 
reproduction and young-raising) are expected on a regular basis. 
These effects could threaten the continued survival of the species. 

■ State and federal wildlife officials express serious concern. 

2.2.3 Impacts on Natural Quiet 

The resource of natural quiet is defined as the natural ambient sound conditions 
found in a park. The NPS has long regarded "natural quiet" as a park resource. 
This perspective is reflected in current public law, in explicit park 
management policy, and by the visitors themselves (§3.1). Just as parks 
contain many tangible features, such as animals, plants, waters, geological 
features, historic buildings and archeological sites, they have intangible 
qualities as well. These qualities include solitude, space, scenery, clear night 



EXECUTIVE SUMMARY: Answers to Questions 



skies, sounds of nature and "natural quiet." Such intangible qualities are 
important components of visitors' overall enjoyment of parks, and are thus 
valued resources. 

Congressional acts and NPS management policy reflect the importance of 
preserving natural quiet in the national parks. 

In developing an approach to preserve natural quiet, the NPS recognizes the 
following five important facts: 

1 . Natural quiet is a resource for preservation within the National 
Park Service mandate. 

2. The human auditory system is an excellent mechanism for 
determining the presence or absence of natural quiet. No readily 
available electronic device can duplicate human hearing for 
identifying audible sounds produced by non-natural sources. 

3 . The difficulty of preserving natural quiet is direcdy related to how 
quiet it is. If the natural ambient sound conditions are relatively 
loud, as along a beach with pounding surf, or near a waterfall, 
then intruding non-natural sounds will have to be comparably 
loud to be heard. On the other hand, in a remote park location 
with no wind or water, or one with little or no vegetation or 
wildlife, even very quiet intruding non-natural sounds will be 
audible. 

4. Humans are not always aware of sounds that are audible. 
Humans, when engaged in any number of activities, may have 
their attention focused on the activity and not be aware that a 
new sound has become audible. Visitors who for the first time 
view the Grand Canyon at Lipan Point are not very likely to 

. remember hearing any aircraft, where only about 30 percent of 

the visitors interviewed reported hearing aircraft (§6.3.1) even 
though roughly 90 percent of them could have. 

5 . Park settings can provide levels of natural quiet that are so quiet, 
there is no sound to be heard except that generated by the 
listener — the sounds of walking, breathing, heart pumping, and 
blood flowing (§3.2.2 and §3.3). 

These five facts have important implications for park management and for 
working to achieve compatibility between use of air space and the underlying 
park lands. First, preserving natural quiet is a park management objective, a 



5. NPS- 7 7, Natural Resource Management Guideline, which addresses protection of aesthetic values, clearly identifies intrusive sounds as affecting an 
aesthetic value of a park and appropriatejor miligative action. NPS-77, Chapter 2, "Protection of Aesthetic Values. " 



10 



2.3 Proper Minimum Altitude 



part of the mission of the NPS, and decisions concerning in which parks and 
in which locations natural quiet is to be preserved are to be made by the NPS. 

Second, if an attentive listener with normal hearing can hear aircraft, then 
natural quiet does not exist while the aircraft is audible. 

Third, achieving natural quiet 1 00 percent of the time, or even a significant 
portion of the day, will not always be achievable, nor will it be necessary, in 
all locations in all parks. There are locations where intruding sounds cannot 
be eliminated. Local street traffic, other visitor activity, as well as aircraft can 
eliminate natural quiet. On the other hand, the studies have shown that 
visitor judgement of the importance of natural quiet varies, probably as a 
function of the type of visitor, and his or her activity (§3.1.4), and hence, 
from the visitor perspective, natural quiet is not equally important in all 
locations or for all visitor activities (a position not necessarily shared by park 
managers). 

2.3 Proper Minimum Altitude 

Establishing a minimum altitude for aircraft overflights over all units of the 
National Park System is neither feasible nor necessary. In those cases where 
significant impacts from overflights have been identified, park management 
objectives and the physics of sound propagation suggest that no single 
minimum altitude can eliminate all aircraft produced impacts. However, 
national park experience with minimum altitude restrictions implies that 
some impacts can be reduced with an appropriately chosen minimum 
altitude. Minimum altitudes have been in force over Yosemite and Haleakala 
National Parks (see 2.4) and are combined with flight-free zones over Grand 
Canyon National Park (2.5). These restrictions have not restored natural 
quiet, but the most egregious impacts have been reduced or eliminated 
where the altitude restrictions have kept aircraft several thousand feet from 
visitors, as at Yosemite, at some locations in Haleakala, and at some sites 
within flight-free zones in the Grand Canyon (§2.3, §9. 1, §9.2). It is clear, 
however, that setting of a minimum altitude for a park, when appropriate 
and approved by the FAA, must reflect park management objectives and the 
elevations of the specific sites that are to be protected. Minimum altitudes, 
or, more accurately, minimum stand-off distances can also reduce the risk of 
impacts on cultural resources (§4.3.4). In any case, however, minimum 
altitudes alone cannot be expected to preserve or restore natural quiet 
(§3.4), or to completely eliminate the adverse effects on all visitors (§6.3. 1). 



11 



EXECUTIVE SUMMARY: Answers to Questions 



2.4 Effects of Minimum Altitudes Established Over Yosemite and 
Haleakala National Parks 

Public Law 1 00-9 1 specified minimum altitudes for aircraft flying (visual 
flight rules) over certain areas of Yosemite National Park and over Haleakala 
National Park. Park management reports that at Yosemite visitor complaints 
about overflights have diminished, and at Haleakala where sound levels have 
been reduced, increased numbers of overflights may have significandy 
negated any improvement the restriction might have made (§9. 1 . 1 and 
§9. 1.2). The lessons learned from these two case studies may be summarized 
as follows: 

■ Raising the minimum altitude to 2000 feet reduces egregious 
impacts and may reduce complaints, but does not effectively restore 
natural quiet. Not only are the lower altitude aircraft audible, but 
high altitude jets are unaffected by such minimum altitudes. 

■ Numbers of overflights have an important impact on length of time 
visitors have an opportunity to experience natural quiet. Unabated 
increases in numbers can negate gains made through increasing the 
distance between aircraft and visitors. 

■ As part of their management strategies, park resource managers must 
carefully consider when and where to preserve natural quiet. 

■ Impacts on natural quiet are likely to be unique at each park, and the 
solutions equally unique. Approaches to problem solving need to be 
flexible to produce effective solutions. 

2.5 Has the Plan for Airspace Above the Grand Canyon 
Substantially Restored Natural Quiet? 

Section 3 of P.L 1 00-9 1 directed the Secretary of the Interior to develop an 
airspace management plan for Grand Canyon National Park (GCNP), to be 
implemented by the Administrator of the Federal Aviation Administration 
(FAA) that would 

". . . provide for substantial restoration of the natural quiet and 
experience of the park and protection of public health and 
safety from adverse effects associated with aircraft overflight. " 

A plan to achieve these purposes, Special Federal Aviation Regulation (SFAR) 
50-2 was implemented in November 1988. In general, SFAR 50-2 regulates 
all aircraft operations below 14,500 feet above mean sea level (MSL) by 
providing four flight-free zones covering about 45 percent ot the park 
(§9.2.2). GCNP monitoring and visitor complaints, measurement ol sound 
levels at various locations throughout the park, surveys ol visitors, and 



12 



2.6 Revisions in the Grand Canyon Airspace Management Plan 



acoustic modeling provided information for evaluating the effectiveness of 
the SFAR (§9.2.3). 

Despite extremely high compliance with the SFAR by aircraft operators, and 
reduced complaints from visitors, aircraft are still audible large percentages 
of the time in much of the park. The SFAR has significandy reduced aircraft 
sound levels for many locations, but natural quiet has not been substantially 
restored. For some visitors, experiencing natural quiet is almost as important 
a reason for visiting the Grand Canyon as is viewing the scenery. Visitors still 
notice aircraft, and believe that the sound has interfered with their 
appreciation of natural quiet, especially in the backcountry, and along the 
river corridor and corridor trail system use zones (§9.2.3). 

Chapter 9 of the full report begins by defining a "substantial" restoration of 
natural quiet to be 50 percent or more (50 to 80 percent) of the park for 
75- 1 00 percent of the time, and concludes that a substantial restoration of 
natural quiet has not been achieved under the current regulation. The 
conclusion is based on acoustic monitoring results and supported by 
computer modeling. Visitor surveys resulted in identifying those visitor 
populations most sensitive to overflights and correlated the percent of time 
aircraft were audible with visitor perceptions. The majority of park visitors 
support 1) maintaining or reducing current amounts of overflight and 2) 
some type of restrictions to meet such policies (§9.2.3). 

Furthermore, computer modeling suggests that if no further actions are 
taken to improve the current regulation, due to projected overflight increases 
(forecasted in the Grand Canyon Airport Expansion Plan), there will be a 
loss in that proportion of GCNP currendy experiencing a substantial 
restoration of natural quiet. Specifically, the proportion of the park 
experiencing a substantial restoration of natural quiet would drop from 34 
percent of the park currendy to less than 1 percent by the year 2010. 
Consequendy, the NPS is compelled to strongly recommend that SFAR 50-2 
be revised to effect and maintain a substantial restoration of natural quiet 
over time (§9.2.3). 

2.6 Revisions in the Grand Canyon Airspace Management Plan 

The NPS recommendation for revision of the Grand Canyon Airspace 
Management Plan is based on the following general concepts (§ 10.3. 10): 

■ Expansion in the size of flight-free zones 

■ Simplification of the commercial tour route structure 

■ Use of temporal restrictions ("no fly" times) 

■ Accommodation of the forecast growth in the air tour industry 



13 



EXECUTIVE SUMMARY: Answers to Questions 



■ Phased-in use of "quiet aircraft technology". 

Computer modeling suggests that this combination of elements will most 
effectively restore natural quiet as mandated by Public Law 1 00-9 1 . A 
reasonable phase-in (15 years) is desirable from all perspectives. The 
modeling takes into account forecast increases in the Grand Canyon air tour 
industry over the next 1 5 years, and incorporates a gradual conversion to 
quiet aircraft over that same time period. 

A summary of the four recommended phases of the plan follows 
(§10.3.10.1): 

Year 1 : Expand existing flight-free zones and create a new flight-free 
zone in western Grand Canyon. This recommendation includes 
combining the Shinumo and Bright Angel Flight-Free Zones into one 
large zone (to be named the Bright Angel Flight Free Zone) and 
expanding it north to the SFAR boundary. The Toroweap/Thunder 
River Flight-Free Zone would be expanded"to better protect the 
Toroweap Overlook area and the Desert View Flight-Free Zone would 
be expanded north and east to better protect the Desert View area. The 
current SFAR 50-2 tour routes and route segments would be reduced 
and adjusted accordingly. Routes within flight corridors would provide 
for one-way traffic only. 

The Dragon Flight Corridor would be abolished, but two quiet aircraft 
routes (one for airplanes, one for helicopters) will exist in this area (the 
new Bright Angel Flight- Free Zone) for five years. This would allow 
those air tour operators who have already invested in quiet aircraft 
technology to be rewarded for their efforts. Traffic ,will be one-way only 
on these two routes. 

The Fossil Canyon Flight Corridor would be realigned and the 
minimum altitude for general aviation aircraft in the Tuckup Flight 
Corridor would be lowered from 10,500 feet MSL to 9,500 feet MSL. 

Year 5: Limit the Fossil Canyon Flight Corridor to quiet commercial 
tour aircraft. The two quiet aircraft routes within the new Bright Angel 
Flight-Free Zone would be eliminated. This action is necessary because 
the computer modeling indicates that having two flight-free zones in 
that area (the current Shinumo and Bright Angel Flight-Free Zones) 
with a flight corridor in-between them (the current Dragon Flight 
Corridor) can not protect or maintain natural quiet adequately over the 
sensitive areas below. 



14 



2.6 Revisions in the Grand Canyon Airspace Management Plan 



Year 10: Limit the Zuni Point Flight Corridor to quiet commercial tour 
aircraft. This means that those companies without quiet aircraft 
technology would only be able to fly over the western part of the SFAR 
or over Marble Canyon. 

Year 15: Limit the entire Special Flight Rules Area to quiet commercial 
tour aircraft. That is, all tour routes would be tlown only with quiet 
aircraft. 

One very important facet of this recommendation would be the 
establishment of an aircraft monitoring program to ensure that the 
substantial restoration is maintained. This program would be designed to 
measure sound levels on the ground in areas where the agency seeks to 
protect natural quiet. The NPS would identify benchmark sites and establish 
a protocol for collecting acoustical data at those sites for the purpose of 
establishing "action triggers". These triggers would specify a noise level that 
should not be exceeded. The NPS would work with the FAA to initiate 
actions which would rectify the situation when the noise level is exceeded. 

The predicted result of the NPS recommendation is that by the year 2010, 
natural quiet would be substantially restored to 64 percent of the park, 75 to 
1 00 percent of the time. Forty-four percent of the park would experience 
natural quiet 100 percent of the time. In contrast, the modeling suggests that 
if "no action" is taken to improve SFAR 50-2, less than 1 percent of the park 
would experience 100 percent natural quiet and less than 10 percent of the 
park would achieve a substantial restoration by the year 2010 (§10.3.10.6). 

It is clear that a "no action" alternative is unacceptable. It is equally clear that 
achieving the substantial restoration mandated by P.L. 100-91 can be 
accomplished only by the proposed restructuring of the airspace with larger 
flight-free zones and the gradual conversion of the air tour fleet to quiet 
aircraft. 

The NPS recommendation offers immediate rewards and long-term 
incentives to those companies which have voluntarily invested in quiet 
aircraft technology and to those companies willing to do so in a timely 
manner. It is important to note that these recommendations will not only 
achieve substantial restoration, but also maintain it in the long term even 
though increases in overflights are forecast. The NPS believes that this 
recommendation strikes an appropriate balance between resource protection 
and visitor enjoyment. 



15 



EXECUTIVE SUMMARY: Answers to Questions 



2.7 Impairment of Visitor Enjoyment 

2.7./ Background 

The effects of aircraft overflights on visitor enjoyment were examined 
primarily through two surveys: the "Visitor Survey" and the "Dose- Response 
Study." The Visitor Survey was designed to provide National Park 
system-wide estimates of visitor impacts, but the results also provide 
valuable information on the variation in effects from park to park. The 
Dose-Response Study examines visitor reactions to overflights of specific 
park locations and provides a quantitative relationship between aircraft 
sound level and visitors' reactions to these sound levels. 

The information from the Visitor SurveyWas obtained through a careful 
five-stage sampling process of park units throughout the system. Interviews 
were conducted of visitors as they left the various selected parks. 
Approximately 1 5,000 visitors were interviewed during the busiest two 
months of the season at 39 parks across the country. 

The Dose-Response Survey included both interviews of visitors and 
simultaneous sound level data measurement. Visitors to four specific sites at 
the Grand Canyon, to one site at Haleakala and to one site at Hawaii 
Volcanoes were interviewed as they left each site. While they were at the site, 
sound levels that they could have heard were measured. Visitors' replies to 
questions about the effects of aircraft overflights were matched with the 
sound levels that were measured while they were at the site. Thus, sound 
levels that could be heard (doses) could be related analytically to visitor 
reactions (responses). 

2.7.2 Impacts Across the National Park System 

Importance of Natural Quiet 

During the Visitor Survey, visitors were asked how important it was to be 
able "to enjoy the natural quiet and sounds of nature" and "to enjoy the 
natural scenery" as reasons for their visit to the park. Visitors were given the 
choice of five possible responses: not at all important, slightly important, 
moderately important, very important and extremely important. Table 2 
summarizes the responses for the park system. System-wide, enjoying natural 
quiet is about as important as viewing natural scenery as a reason tor visiting 
national parks (§6.2.1). 



6. Excluding park units in Alaska. 



16 



2. 7 Impairment of Visitor Enjoyment 



TABLE 2: IMPORTANCE OF NATURAL QUIET AND NATURAL SCENERY 
AS REASONS FOR PARK VISIT 


Reason for Park Visit 


Estimate 


95% Confidence Interval 


Enjoy Natural Quiet 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n=15,150) d 


90.7% 
397.1 M 
1.23 


88.3% to 93.1% 
386.6 M to 407.6 M 


View Natural Scenery 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n=15,227) d 


93.2% 
408.0 M 
0.98 


91.3% to 95.1% 
399.7 M to 416.3 M 


Respondents who answered 3, 4, or 5 on the following scale: 1 =not at all, 
2=slightly, 3 = moderately, 4=very, and 5=extremely. 

Estimate of the 1992 visitor population is 437.8 million visitors. As used here, 
"visitor" means one person exiting the park. Hence, if a person enters and 
leaves a park once each day for three days, that person is counted as three 
"visitors". 

°Standard error is of the percent, not of the number of visitors. 
Number of completed interviews. 



Impacts Produced by Hearing and Seeing Aircraft 

Visitors were asked if they heard or saw any aircraft during their visit, and if 
they did, whether the aircraft interfered with their enjoyment, whether they 
were annoyed, and whether the aircraft interfered with their appreciation of 
the natural quiet and the sounds of nature. Table 3 summarizes the results 
for the park system. About one fifth of all visitors to the national parks 
(about 80 million visitors a year) remember seeing or hearing aircraft during 
their visit to the park, and about 2 to 3 percent of all visitors, or roughly 7 to 
1 3 million visitors annually, can be expected to be impacted by hearing or 
seeing aircraft (§6.2.2). 

Impacts Among Different User Groups Produced by Hearing 
Aircraft 

Impacts of overflights on different user groups were also examined. Three 
visitor groups were identified: frontcountry, backcountry, and overnight 
backcountry permit holders. Visitors who completed the exit survey could be 
categorized based on their primary recreational activity. Those who indicated 
their primary activity was backpacking or hiking were classified as 
"backcountry" users, while all other surveyed visitors were classified as 
"frontcountry". The third group, the backcountry permit group, is a sample 
of permit holders from those NPS units that require a permit to stay 
overnight in the backcountry. These permit holders were surveyed by mail. 



17 



EXECUTIVE SUMMARY: Answers to Questions 



TABLE 3: NUMBERS OF VISITORS HEARING OR SEEING AIRCRAFT, 
AND THE RESULTANT IMPACTS 


Type of Effect 


Estimate 


95% Confidence 
Interval 


Heard Aircraft 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n= 15,1 90) 


20.1% 

88.0 M 

5.10 


10.1% to 30.1% 
44.2 M to 131.8 M 


Saw Aircraft 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n = 15,081) 


18.8% 

82.3 M 

4.10 


10.8% to 26.8% 
47.3 M to 116.3M 


Hearing Aircraft Interfered with 
Visitor Enjoyment 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n = 15,150) 


1 .9% 
8.3 M 
0.65 

IM 


0.6% to 3.2% 
2.6Mtol4.0M 


Annoyed by Hearing Aircraft 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n = 15,1 74) 


1 .6% 
7.0 M 
0.77 


0.1% to 3.1% 
0.4 M to 13.6 M 


Hearing Aircraft Interfered with 
Appreciation of Natural Quiet 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n= 15,049) 


2.8% 

12.3 M 

0.99 


0.9% to 4.7% 
3.9 M to 20.6 M 


Annoyed by Seeing Aircraft 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n= 15,072) 


3% 

13.1 M 

0.86 


1.3% to 4.7% 
5.7 M to 20.6 M 


See notes to Table 2. 



Figure 1 shows the percentages of visitors in each of the three groups who 
remembered and reported hearing aircraft, who were annoyed, who 
indicated aircraft sound interfered with their enjoyment, and who indicated 
aircraft sound interfered with their appreciation of natural quiet and sounds 
of nature. A higher percentage of backcountry than frontcountry visitors 
report hearing aircraft and are more likely to experience impact from these 
aircraft. Though the reasons for these differences have not been identified, it 
is clear that hiking and backpacking do not remove visitors from the impacts 
of overflights (§6.2.3). 



18 



2. 7 Impairment of Visitor Enjoyment 



Visitor Impacts Among User Groups 
Exit and Mail Survey Results 



100 
90- 
80 • 
70 
60- 
50- 
40 
30 
20 
10 





_M 



m. 



^^^1 



:■;:;■•:;:;:. 



Head Aircraft 



Annoyed 



Interfered w/ 
Enjoyment 



Interfered w/ 
Natural Quiet 



^^■1 Exit Survey Frontcountry Activities (n = 6,976) 
^vw Exit Survey Bockcountry Activities (n= 1 ,928) 
£:•&•:■:■:•! Bockcountry Permit Holders (n = 91 1) (Mail Survey] 

Note: Data are from 23 of the 39 Visitor Survey parks where bockcountry permits are required for an 
overnight stay. 



Figure 7 : Impacts of Hearing Aircraft Among Different Visitor Groups 



2.7.3 Impacts at Specific Parks 

The Visitor Survey information summarized above was collected at 39 
different units of the National Park System. Examining results from these 
individual parks provides an indication of the wide variation in aircraft 
impacts from park to park. Figure 2 is based on the visitor survey data and 
shows estimates of the number of visitors who heard aircraft and the number 
who were annoyed at each of the parks during the two month survey period. 
The numbers next to the plotted points refer to the specific park as given in 
Table 6.5 of the full report, and Table 4 lists the specific parks of Figure 2 
having more than 1 0,000 visitors annoyed by aircraft during the survey. (As 
above, see notes to Table 2, visitors are counted as annoyed if they answer 3, 
4, or 5 on the following scale: 1 = not at all, 2 = slightly, 3 = moderately, 
4=very, and 5 =extremely.) Park visitor reports of exposure to aircraft 
(hearing aircraft) and of impacts from the exposure vary widely from park to 
park, and the system wide results summarized in Table 3 can not capture the 
nature and severity of impacts that may occur at specific parks (§6.3. 1). 



19 



EXECUTIVE SUMMARY. Answers to Questions 



Number Annoyed vs Percent Who Heard 

(Number During 2 Month Survey) 




oU,UUU" 

9 

i 60,000- 
< 

S 40,000- 
"o 

SI 

I 20,000- 


: - : 






























* 

■ ■ 




" 


m 


m 






'■"*"■ 

» ■ ■ : 
















Number of Visitors Who Heard AC 





Figure 2: Numbers of Visitors Hearing Aircraft and Annoyed 
by Aircraft at Visitor Survey Parks 



TABLE 4: VISITOR SURVEY PARKS WITH MORE THAN 10,000 VISITORS 


IMPACTED BY OVERFLIGHTS DURING SURVEY 


National Park Unit 


5 


Cape Cod National Seashore 


11 


Everglades National Park 


15 


Glacier National Park 


16 


Glen Canyon National Recreation Area 


17 


Grand Canyon National Park 


18 


Great Smoky Mountains National Park 


19 


Gulf Islands National Seashore 


20 


Haleakala National Park 


21 


Hawaii Volcanoes National Park 


24 


Lake Mead National Recreation Area 


27 


Mount Rainier National Park 


28 


Mount Rushmore National Monument 


29 


North Cascades National Park 


35 


Sleeping Bear Dunes National Lakeshore 


38 


Yellowstone National Park 


39 


Yosemite National Park 



2.7.4 Impacts at Specific Sites 

Though the Visitor Survey provides much useful information about the 
impacts of overflights system wide and about impacts at the specific surveyed 
parks, it was not designed to collect any quantitative information about the 
actual sounds that visitors could have heard. It therefore provides no means 
for answering questions that would help quantify the relationship between 
visitor impacts and aircraft sound level. Since the Visitor Survey could not 
provide any information about sound levels experienced by visitors, the 



20 



2. 7 Impairment of Visitor Enjoyment 



Dose-Response Study was designed and conducted to answer the following 
three questions: 

1 . Does impact as reported by visitors depend upon sound levels 
produced by aircraft overflights? 

2. If so, what is the relationship between reported impact and 
aircraft sound levels? 

3. What factors other than aircraft sound affect visitor impacts? 

Figures 3 and 4 present dose- response curves that were developed from the 
data collected at five specific sites. In each, the horizontal axis gives the dose, 
while the vertical axis gives the response, and the curves show the 
relationship between the two. The two figures are for two doses and one 
response. 



Moderate to Extreme Annoyance 
lue to Aircraft Noise in a Park Environment 



too 

90 
80 
70 
60 
50 
40 
30 
20 
10 
















- 


^ Region of survey doto 
■■•Extrapolation 






















.... 


























: Hermit Basin.: 


V 


• **: 


.... 






..;••■; 




Wahaula- o 
■ • : Point Imperial ■ :\irf>""*/ 
Lipan Po\n\^^*^^~J^" 






• w* * 


1 — 


-=-: 




- 1^1 _ _ 'if 


5=^± 




iS^^^^zL. 





4 6 8 10 20 40 

Percentage of Time Aircraft are Audible 



60 80 100 



Figure 3: Dose-Response Curve for Visitor Annoyance vs 
Percent of Time Aircraft are Heard 



Moderate to Extreme Annoyance 
due to Aircraft Noise in a Park Environment 



100 r 




10 20 30 40 50 60 70 80 

Hourly Equivelent Sound Level (L e q. 1 hr) of Audible Aircraft (dB) 



Figure 4 : Dose-Response Curve for Visitor Annoyance vs 
Hourly Equivalent Sound Level 



21 



EXECUTIVE SUMMARY: Answers to Questions 



The doses are percent of time aircraft are audible, and hourly equivalent 
level, Leq,ihr for audible aircraft . The response is percent of visitors who 
said they were annoyed by aircraft noise while at the site . The solid portion 
ot the curve shows where the data lie, the dashed portions are extrapolations 
based on analysis. The dose-response curves, to the extent that they are 
applicable to a given site, can be used to predict visitor responses (impacts) 
by measuring (or predicting) dose. For example, if monitoring at a site 
similar to Sliding Sands shows aircraft audible about 30 percent of the time, 
then Figure 3 predicts that about 32 percent of the visitors will be annoyed. 
Alternatively, if Leq,ihr of 40 dB from audible aircraft were measured or 
predicted for the site, Figure 4 shows that about 37 percent of the visitors 
will be annoyed. Hence, visitors report negative reactions to the sound of 
aircraft at specific sites, and these negative reports increase as exposure to 
aircraft sounds increase (§6.3.2). 

These curves demonstrate that sound exposure, though an important 
variable, is not the sole determinant of impact oil visitors. Not only do the 
impacts on visitors clearly vary considerably from one site to another, but 
statistical testing of the data has shown that several other specific factors 
affect visitor response. Though the importance of these factors varies 
depending upon which dose and which response are examined, some 
generalizations are possible. First time visitors to a site are less sensitive to 
aircraft sound than are repeat visitors; visitor "groups" of one or two people 
are more sensitive than are larger groups; visitors who thought enjoying the 
natural quiet and sounds of nature was a very or extremely important reason 
for visiting the site were more sensitive to aircraft sound than visitors who 
judged quiet and sounds of nature as less important. Other factors may also 
be important in affecting how visitors respond, but lack of data prevented 
developing statistically verifiable results. The type of site is clearly important, 
since the curves vary from site to site; what is unknown is what 
characteristics of the site are important. 

2.7.5 Identification, Analysis and Mitigation of Impacts 

When used in conjunction with NPS management judgement, the 
dose-response results provide a means for quantitatively identifying and rank 



Percent of time aircraft are audible, while simple to measure, is extremely difficult to predict. On the other hand, measurement oJL C n,iUr of audible 
aircraft is somewhat difficult, but reasonably easy to predict with current available computer models. Hence, dose-response curves for both metrics have 
been developed to provide the tools necessary Jor measurement, analysis and mitigation of overflight noise problems in parks. 

The response of annoyance rather than interference with enjoyment was chosen Jor two reasons. Primarily, annoyance is the metric of response that has 
been used Jor almost two decades to assess the impact of intruding sounds, and particularly aircraft sounds on humans. The use of annoyance thus 
continues a well-established approach. Second, visitor impact in terms of annoyance and in terms of interference with enjoyment have proven to be 
virtually identical, see Jor example Table 6. 5 in Chapter 6 ofthejull report. Curves were also developed Jor the dose of interference with the natural quiet 
and sounds of nature. 



22 



2. 7 Impairment of Visitor Enjoyment 



ordering sites within parks that potentially produce significant impacts on 
visitors. The Visitor Survey shows that impacts on visitors do occur, but to 
very different degrees at different parks. The NPS has developed a ranking of 
SO to 100 parks with potential overflight produced problems. Using these 
NPS identified parks, candidate sites within the parks should be identified 
where visitors may be impacted, and with the proper data collection process, 
the dose-response curves can be used to determine the sites with significant 
problems. 

Park personnel will collect time audible data, using a carefully designed 
sampling procedure, and compare the results to the appropriate curve to 
estimate the degree of impact. The NPS will set criteria for acceptable 
degrees of impact, identifying both maximum acceptable percentages and 
maximum acceptable numbers of visitors impacted for each type of site or 
activity. If these maximums are exceeded, the NPS will initiate a process of 
analysis and interaction with aircraft operators and other agencies (eg., the 
Federal Aviation Administration, the Department of the Air Force, etc.) to 
eliminate or reduce the impacts. 

The criteria for maximum acceptable impact will be developed by the NPS in 
terms of both percent of visitors to a site and numbers of visitors to a site. 
In terms of percent of visitors, a maximum acceptable value of between 20 
and 30 percent will be identified. For example, where park measurements 
show a dose that results in more than 25 percent of visitors impacted, 
analysis and mitigation efforts will commence. Maximum acceptable 
numbers of visitors impacted will also be identified. 

A flexible approach to analysis and mitigation will be developed and pursued. 
In some cases, for example, discussions with aircraft operators may identify 
simple changes (for example re-routings of air tours) that can be tested, 
found to provide acceptable reductions of impact, and implemented. In 
other cases, detailed analyses of many alternatives may be necessary. In such 
cases, the simple time audible metric can no longer be used. This metric, as 
mentioned, is extremely difficult to predict, and the alternative 
dose-response curves using hourly equivalent sound level, Leq,ihr, of audible 
aircraft will be employed. 

Detailed analyses of aircraft produced sound levels have long been conducted 
for airports and military air facilities. These efforts have resulted in computer 
models that can predict, generally within acceptable tolerances, how sound 
levels on the ground will be altered by changes in airspace use. These models 
are being adapted or expanded to provide predictive capabilities for aircraft 
overflights of parks. Using these computer models and information about 
airspace use including aircraft types, number of flights per day, location of 
flight corridors, altitudes of flights and terrain features, Leq,ihr can be 
computed for current operations and predicted for future or proposed 



23 



EXECUTIVE SUMMARY: Answers to Questions 



operations, and appropriate dose-response curves and criteria can be used to 
estimate resulting visitor impacts. 

2.8 Impacts on Safety 

In the survey of 98 parks, a substantial majority of managers had slight or no 
concern about safety risks posed by overflights, and believed that both 
visitors and staff felt little or no threat to their safety from aircraft (§7.1). 
However, managers at 16 parks perceived that aircraft overflights 
represented a serious or very serious safety problem. The managers specific 
concerns ranged from perceptions that mid-air collisions were a problem, to 
safety of visitors on the ground, to possibility of collision with landmarks, to 
disruption of trail horses. 

The survey of visitors revealed that virtually no visitors perceived any safety 
risk posed by aircraft overflights (§8.2). Some outdoor recreation 
organizations indicated concern, and it is likely that ensuring separation of 
helicopter overflights and horse traffic would provide some benefit (§7.3). 
Temporary flight restrictions (TFR's) around forest fires do not seem to have 
prevented airspace conflicts, and the Bureau of Land Management, U.S. 
Forest Service, Department of the Interior, Federal Aviation Administration 
and the Department of Defense are all developing improved means for 
communicating TFR information to pilots (§7.4). 

2.9 Values Associated with Overflights 

Value to NPS 

The values or benefits of administrative and air-tour flights were examined. 
Sixty-five percent of the 98 parks with potential overflight problems report 
using aircraft in an administrative capacity, and by far, the greatest amount of 
flying time is spent fire fighting using helicopters (§8.1). In general, 
however, managers reported that the overflights by aircraft on park 
administrative purposes make up a small fraction of all overflights (§2.1.4). 
It is clear that national parks and visitors benefit trom administrative 
overflights. 

Value to Visitors 

Many people take air tours over national parks, including approximately 
750,000 people visiting the Grand Canyon in 1992, and perhaps nearly as 
many in Hawaii. A questionnaire was mailed to passengers ol tour Grand 
Canyon tour operators, and three Hawaiian tour operators. The sample ol 
air tour passengers (555 responded) cannot be considered as truly 
representative since there is no confidence that it was a random sample. 



24 



2. 9 Values Associated with Overflights 



Consequently, results cannot be used to make generalizations about 
sightseeing passengers at Grand Canyon National Park, the Hawaiian 
national parks, or to air tour passengers overflying the National Park System 
as a whole. 

A significant majority of responding air tour passengers reported that the 
flight was very or extremely enjoyable, very much or extremely increased 
their appreciation of the park, and would recommend the flight to others. 
More than 95 percent of the respondents were first time air tour passengers, 
and while about 90 percent of the Grand Canyon air tour passengers also 
visited the canyon on the ground, fewer than 30 percent of the Hawaii tour 
passengers also visited the park on the ground (§9.2.1). 

By far the most important reason for taking an air tour, identified by about 
6 5 percent of the passengers surveyed, was to see the park from a unique 
perspective. The second most important reason, identified by about 20 
percent, was limited time. Fewer than 1 percent of the passengers 
identified each of the following reasons: "experience a unique activity", 
"health or physical disabilities", or "other" reasons. Finally, when asked 
whether the benefits of air tours to passengers outweigh the disturbances to 
park visitors, about 55 percent of the passengers agreed or strongly agreed, 
about 30 percent were neutral, and the remaining 15 percent disagreed or 
disagreed strongly. 

Values to Local Economies 

Limited information is available on the economics of air tourism in the 
United States, especially as it relates to national parks. It is privileged 
economic data that the FAA does not collect. Based on industry reports, the 
economic impact of Grand Canyon air tours alone is two hundred and fifty 
million dollars ($250,000,000). The industry in Hawaii is apparendy very 
nearly as large, and there is a sizable industry in other parts of the country 
including New York, St. Louis, and Southeastern Alaska. The FAA estimates 
that there are at least 1 87 air tour operators across the nation. This suggests 
the total economic impact of the industry is in the range of one-half to 
three-quarters of a billion dollars a year. 



3 Conclusions 

Between 30 and 40 non-Alaskan parks are current priorities for research and 
problem-solving with respect to aircraft overflights. The problems may differ 
considerably from park to park and developing solutions will require detailed 
knowledge of specific park conditions. Where are the most sensitive park 
areas? Where do aircraft fly in relation to these areas? What types and 



25 



EXECUTIVE SUMMARY: Conclusions 



numbers of aircraft fly over the park, and who operates them? Where do the 
most serious impacts occur? Local park personnel need to gather 
considerable information in order to work knowledgeably toward solutions 
with aircraft operators, but the information collected needs to be reliable, 
related to what is known about the impacts produced by overflights, and 
useful in developing solutions. Reliability, relevance and usefulness can be 
assured by uniform application of the information presented in this report. 
Such information appears to be adequate to develop uniform methods of 
data collection and analysis, impact reduction alternatives, and methods for 
implementation and monitoring. The details of overflight problems and their 
solutions are local, but the process and general methods for problem 
identification, analysis and resolution must be uniform throughout the 
National Park System. 

For example, research has shown that simple listening for aircraft, conducted 
with well-defined logging and sampling procedures, will determine not only 
the amount of time that natural quiet exists, but, by using the dose-response 
results, can estimate the impacts of overflights on visitor annoyance and on 
visitor perception of interference with the appreciation of natural quiet. 
Uniform guidelines developed from the research reported here will help 
local park management assess not only probable impacts on natural quiet and 
on visitors, but on historic or cultural structures, and on wildlife. Such 
information can help define the degree of the problem and, by deduction, 
may suggest how difficult solutions may be. 

Because the details of problems are park specific, and because the NPS 
recognizes that air travel is an essential part of the nation's life, no single 
minimum altitude can be identified for the entire national park system. 
Minimum altitudes, or more properly, minimum stand-off distances, can be 
useful to eliminate the severest impacts, but unless very large, are unlikely to 
restore natural quiet. A 2,000 foot minimum altitude, such as in the current 
FAA advisory for overflying national parks, is useful but should not stand 
alone as the solution to park overflight issues. 

The enthusiasm and enjoyment engendered in air tour passengers by their 
experience overflying national parks has serious implications for the NPS. 
Such customer satisfaction and apparent associated demand for air tours 
suggests growth potential for the air tour industry. The NPS must anticipate 
that air tour operations will continue to expand, not only over parks 
currendy overflown, but at parks presendy free of any significant overflight 
activity. A process must be established for the park service to participate 
early in the establishment of air tours over parks, and to interact in a way 
that can influence decisions about where and under what conditions new air 
tours operate. 



26 



4. 1 Recommendot/'on 7 



Finally, though SFAR 50-2 has greatly improved the sound environment in 
areas of the Grand Canyon, natural quiet has not been substantially restored, 
and further improvements to the regulation are essential to achieve the 
substantial restoration of natural quiet mandated by Public Law 1 00-9 1 . 



4 Recommendations 
4.1 Recommendation I 

Develop Airspace/Park Use Issue Resolution Processes 

The NPS recommends that the Department of Transportation — 
Department of the Interior Interagency Working Group be maintained as a 
functioning entity to manage interagency problem solving through to the 
operational level of both agencies. Their priorities should be to identify and 
document processes that can be clearly communicated to field offices where 
problem solving should occur. Although many of the recommendations that 
follow are tied to this process, there may be some airspace/park use issues 
that go beyond the scope of the following recommendations. The general 
shape of this process should be as follows: 

■ Define and report issues in a format agreed upon by the agencies, 
including definitions of impacts oudined in this report. 

■ Forward information to points of contact in NPS and FAA who 
would be expected to seek resolution of the issues. 

■ Specify the time period during which a resolution must be achieved. 

■ Issue a joint report to the Interagency Working Group on success of 
resolution or mitigation efforts. If resolution is not possible, the 
issues would be addressed by the policy group. 

■ Issues not resolvable by the Interagency Working Group would be 
forwarded to the Secretaries of Transportation and Interior for final 
resolution. 

The NPS also recommends that NPS and DOD use the newly established 
Federal Interagency Airspace/Natural Resources Coordination Group to 
develop similar issue resolution processes for low-level military overflights. 



27 



EXECUTIVE SUMMARY: Recommendations 



4.2 Recommendation 2 

Establish and Maintain Agency Points of Contact 

The NPS strongly recommends that agency points of contact be officially 
established and maintained as follows: 

NPS — Deputy Director and Overflight Studies Coordinator 

FAA — Air Traffic Operations (AAT), Flight Standards (AFS), and 
Environment and Energy (AEE). 

DOD — To be requested through the new Federal Interagency 
Airspace/Natural Resources Coordination Group. 

4.3 Recommendation 3 

Use the Full Range of Methods and Tools for Problem Solving 

The NPS recommends that all reasonable methods and tools be used in 
airspace/park use issue resolution processes. The following is a partial list of 
methods, any of which might be reasonably effective, feasible, and verifiable 
for use on a specific situation. The NPS has developed tools that permit 
identification of locations impacted by overflights, that compute, in terms of 
sound levels, the effects of changes in aircraft operations and that can be 
used to measure the reductions in impacts that result from such changes. 
The tools are based on a number of studies including, dose-response results, 
simplified sound level measurement techniques and computer programs that 
estimate sound exposure results from aircraft overflights. 

The partial list of methods includes the following: 

Voluntary Agreements: Voluntary agreements can have a role in 
resolving or mitigating airspace/park use issues if some fundamental 
weaknesses can be addressed. The FAA, the NPS, and air tour operators 
need reasons to enter into these agreements. Furthermore, there are no 
enforcement or penalties involved should operators withdraw trom or 
refuse to participate in agreements. If rulemaking and penalties result 
when voluntary agreements do not work, then all parties will have 
incentives to make and comply with these agreements. 

Incentives to Encourage Use of Quiet Aircraft: NPS research 
suggests that quieter aircraft can play an important role in substantially 
restoring or maintaining natural quiet in parks. Although there is no 
Federal requirement for air tour types of aircraft to be manufactured to 
produce less noise than Stage 3 standards for large commercial aircraft, 
some aircraft are significandy quieter than others and more appropriate 



28 



4.3 Recommendation 3 



for use in air tour operations. Because of the significant expense, 
incentives need to be developed to encourage air tour operators to 
replace equipment with quieter aircraft. Internally, the NPS will need to 
work with the Department of the Interior's Office of Aircraft Services to 
also provide incentives for parks to use quiet aircraft. P.L. 102-581, an 
"Act to amend the Airport and Airway Improvement Act of 1982 to 
authorize appropriations, and for other purposes, " requires the FAA to 
identify "any measures to encourage or require the use of quiet aircraft 
technology by commercial air tour operators." 

The NPS defers to FAA expertise on this subject, but strongly 
recommends that FAA facilitate the introduction of quiet aircraft 
technology to benefit national parks, among many others. 

Spatial Zoning: Flight-free zones and flight corridors have been 
implemented in the Grand Canyon with some success. Experience has 
shown that, to preserve or restore natural quiet, flight-free zones must 
be quite large in extremely quiet places, approximately 20-30 miles 
minimum dimension. The problem, discussed in Chapter 3 of the full 
report, is that some park environments are so quiet that the sound of 
aircraft can be heard at great distances from flight paths. 

Altitude Restrictions: Minimum altitudes can help, but for tour 
aircraft or low-altitude military training, the altitudes necessary to 
significandy reduce impacts may essentially defeat the purpose of the 
overflight. On the other hand, altitude restrictions used in Yosemite and 
Haleakala have helped to reduce the most egregious impacts even 
though overflight impacts have not been eliminated. 

Operating Specifications for Operators: As part of its certification 
processes, FAA may require operators to conform with certain 
operational requirements. These requirements generally identify the 
types of operations authorized, the types of airplanes permitted, airports 
authorized for use and time limitations for maintenance, and training. 
Operations specifications that relate direcdy to park overflight 
operations may provide a reasonable method to address some 
documented adverse effects of overflights. 

Treatment of Air Tour Operations as Concessions: National parks 
treat all commercial services provided to -visitors in parks as concessions 
(i.e. regulated industries) which insures services will conform to 
minimum standards, are not priced unreasonably, and are consistent 
with park values. In some ways, air tour operations are similar to 



The FAA is awaiting completion of the NPS Report to Congress before it completes the report required by the Airport and Airway Safety, Noise 
Improvement, and Intermodal Transportation Act of I 992. 



29 



EXECUTIVE SUMMARY: Recommendations 



ground-based services. In fact, where airstrips are inside parks, the NPS 
has several air tour operations under concession permit. It a joint 
FAA-NPS permitting process can be developed, similar arrangements 
may be possible where it is determined that air tour operations use the 
resources of the national parks. The purpose of this is to reduce 
resource impacts and to provide a specific visitor service. 

Noise Budgets: Noise budgets have been used at some airports 
(Denver- Stapleton was one of the first) to allot responsibility for and 
control of noise among operators. Such budgets assume that the total 
noise generated by the airport, and by each operator, can be quantified. 
Each operator can be allocated an amount of "noise," generally based on 
an existing or previous level of operations. If an operator uses quieter 
aircraft, through retrofit or new purchases, more flights can be 
conducted while staying within the budget. Budgets are negotiated 
rather than imposed. Noise budgets may provide a means for limiting 
growth in air tour traffic over parks in that they focus on the goal of 
limiting or reducing the impact of the sound of overflights, not on 
direcdy limiting the number or type of aircraft operations. A draw-back 
for park application may be the need for tracking numbers of operations 
by time and type of aircraft. Another drawback is that adverse effects to 
visitor experience may not necessarily be addressed. 

Limits on Times of Operations: Some sensitive areas on the ground 
may have cyclical daily, weekly or seasonal high and low visitation 
periods. Aircraft operations may be timed to coincide with low use 
periods. Alternatively, air tours may have slow days, periods or seasons, 
and visitors in search of tranquillity and natural quiet could be informed 
of the best times to visit the park and avoid significant numbers of 
overflights. Limited "No Fly" periods could provide visitors with 
certainty of natural quiet in some parks and should be further evaluated. 

4.4 Recommendation 4 

FAA to Address High Priority NPS Airspace/Park Use Issues 

The NPS recommends that NPS/FAA/DOD joindy commit to resolving and 
mitigating airspace/park use issues beginning with identified priority areas. 
Such a commitment may enable the agencies to develop and more effectively 
communicate how issues can be resolved at the local level. 

4.4. 1 NPS Managerial Priorities 

NPS believes its managers' identification of areas with aircraft overflight 
problems is a relatively accurate indicator of where airspace/park use issues 



30 



4.4 Recommendation 4 



exist. There is basic congruence between manager and visitor perceptions. 
Many of the 98 areas identified by managers have some type ot 
overflight-related problem. Mitigation is possible for some areas and unlikely 
for others. The NPS seeks resolution of its top priorities and recognizes that 
the others (See Appendix B of the full Report) merit further investigation as 
well. Based on top priority NPS areas for resolution of airspace issues 
include: 

Grand Canyon National Park 
Hawaii Volcanoes National Park 
Holeakala National Park 
Great Smoky Mountains National Park 
Glacier National Park 
Bryce Canyon National Park 
Bandelier National Monument 
Statue of Liberty National Monument 

The NPS will further evaluate the complex air traffic patterns over Yosemite 
National Park and Cumberland Island National Seashore to see if mitigation 
appears to be possible and will then discuss those situations with FAA. 

4.4.2 NPS Priorities for Protection of Natural Quiet 

The following is a list of parks where the NPS believes maintaining or 
restoring natural quiet is an immediate priority. Natural quiet is an 
increasingly scarce resource in the United States. There ought to be national 
parks where this can be experienced. Criteria for the selection of these areas 
is listed in section 10.3.6 of the full Report. Highest priority areas meeting 
these criteria include: 

Glacier National Park 

Zion National Park 

Southeast Utah Group Parks 

Haleakala National Park 

Crater Lake National Park 

Isle Royale National Park 

Mesa Verde National Park 

Rocky Mountain National Park 

Chaco Cultural National Historical Park 

The NPS will work with the FAA to further refine the criteria and how they 
may apply to other parks. 

4.4.3 NPS Priorities for Resolution of Safety Concerns 

The NPS recommends that its perceived on-ground safety concerns related 
to overflights be investigated by FAA to see if these problems can be resolved 
or mitigated. The FAA and the NPS are cooperating in an effort to identify 
and put into effect recommended air tour patterns and altitudes that will 



31 



EXECUTIVE SUMMARY: Recommendations 



enhance aviation safety around the Statue of Liberty and reduce other 
impacts there as well. Additionally, the FAA is developing a Special Federal 
Aviation Regulation that will improve the safety of commercial air tour 
operations in Hawaii through establishing minimum altitudes, minimum 
standoff distances, and additional safety measures. The priorities for the NPS 
include: 

Statue of Liberty National Monument 

Hawaii Volcanoes National Park 

Perry's Victory Memorial & International Peace Park 

The process exists for the FAA to use its authority and expertise to resolve 
reported safety issues. These and any other issues that are identified by park 
managers will be forwarded to the FAA for investigation and resolution 
through the FAA's compliance and enforcement program. 

4.4.4 NPS Priorities for Problem Solving with Department of Defense 

The NPS recommends that NPS and DOD agencies explore resolution of 
airspace issues at the following priority areas through the Federal Interagency 
Airspace/Natural Resources Coordination Group. It will be important for the 
FAA to be involved in this process as well. This group will report to their 
respective policy representatives by the end of 1994 on recommendations 
for resolving existing and potential airspace conflicts. NPS priorities for areas 
to be examined during this search for procedures include the following: 

Congaree Swamp National Monument 
Sequoia-Kings Canyon National Parks 
Organ Pipe Cactus National Park 
Death Valley National Park 
Channel Islands National Park 
Joshua Tree National Park 
Petrified Forest National Park 
Pu'ukohola Heiau National Historic Site 
Gulf Islands National Seashore 

South Florida parks (Everglades National Park/Big Cypress National 
Preserve/Dry Tortugas National Park 

DOD is required to report back to the Senate Armed Services Committee on 
development of procedures to resolve airspace/park use issues by January 1 , 
1995. The NPS will also report to the Subcommittee on National Parks, 
Forests, and Public Lands as well as to the House and Senate Armed Services 
Committees on the success and utility of this approach to problem solving. 



32 



4.6 Recommendation 6 



4.5 Recommendation 5 

Develop a FAA Operational Rule Triggered by NPS 

The NPS recommends that FAA develop an operational rule to regulate air 
tour operations where they have or may have adverse effects on national 
parks. If voluntary agreements are not adequate, the NPS should be able to 
trigger action by the FAA to delineate aerial sightseeing areas defined by FAA 
Handbook 92.01 for Principal Operations Inspectors. The NPS would 
forward recommendation on the size, altitudes and routes to effect noise 
abatement and mitigate impacts to persons and property on the ground in 
parks. The FAA may adjust the recommendations and incorporate them into 
tour operators' operation manuals. The rule would need to specify that tour 
operators operate in accordance with Part 135 FAA Regulations. Any request 
by an operator to the FAA to fly below 2,000 feet or within 2,000 feet 
horizontally of sensitive areas and structures would need clearance from the 
FAA only after coordination and concurrence by the park manager. 

This rule would minimize the effect on other types of aviation by targeting 
specific problem areas. The rule's existence would facilitate the use of 
voluntary agreements. The NPS recommends FAA consider a special 
sub-part of 1 35 regulations to be developed for air tour operations. 

Areas where this rule is most needed include the national parks in Hawaii, 
Glacier National Park, Canyonlands National Park, Great Smoky Mountains 
National Park, Zion National Park, Bryce Canyon National Park, and Rocky 
Mountain National Park. 

4.6 Recommendation 6 

Develop a FAA Rule to Facilitate Preservation of Natural Quiet 

The NPS recommends that FAA, under the authority of Section 6 1 1 of the 
Federal Aviation Administration Act, implement a rule which would 
provide for the protection of natural quiet. 

Several nationally applicable environmental statutes and regulations recognize 
that there are circumstances where special protection — beyond ordinary 
performance standards or requirements — may be necessary to adequately 
protect nationally significant resource values. 

Class I Designations under the Clean Air Act require new air pollution 
sources which may affect designated airsheds — including many in national 
parks — to prevent significant deterioration of existing air quality so that 



10. 49U.S.C. Section 611 (b)(1) 



33 



EXECUTIVE SUMMARY: Recommendations 



resources including air quality-related values such as scenic vistas are not 
adversely affected. The absence of air pollution in some areas is what makes 
us aware of air pollution in others; if all areas are equally polluted, we have 
no way to know what is natural. Most Class I areas are at least 5,000 acres in 
size. 

Outstanding National Resource Waters (ONRW) designations under 
the Clean Water Act often mean that no new point source discharges ot 
pollutants are permitted in streams or other water bodies designated as 
ONRW. Waters in national parks are specifically referred to in the regulation 
that implements ONRW and several states have designated ONRW in parks. 
Their overall purpose is to keep the cleanest of the nation's waters clean. 

The provisions of Section 522, Designating Lands Unsuitable for all or 
certain types of mining, of the Surface Mining Reclamation and Control Act, 
allow for the protection of unique resources, such as those in the National 
Park System, by prohibiting all or certain types of coal mining in certain 
areas. In one such designation, the Secretary oPthe Interior found some 
Federal lands adjacent to Bryce Canyon National Park to be unsuitable for 
surface mining because of the potential for adverse effects to scenic resources 
and quiet. 

Each process shows that what is generally applicable may not adequately 
safeguard the unique resources and attributes of special, nationally significant 
lands and that as a consequence, designations or categories need to be 
implemented that establish a higher standard of protection. The NPS 
believes that there are parallels between these processes and 
overflight- related adverse impacts to units of the National Park System. 
Practices that are generally suitable for aircraft elsewhere may not be suitable 
in a limited number of cases where natural quiet or especially sensitive 
cultural resources or threatened or endangered species can be adversely 
affected by overflights. The NPS believes the following criteria can provide a 
starting point for establishing a similar process for outstanding natural quiet 
parks: 

Critical habitat for an endangered species known to be adversely affected by 
noise (e.g., the grizzly bear in the lower 48 states). Excessive and avoidable 
noise could be found to be an adverse modification of habitat. 

■ Seriousness and solemnity of purpose characterizes the park unit or a 
portion thereof and the sights and sounds of overflights can diminish 
the ability of visitors to experience — with respect and reverence — 
the resources and values embodied in selected Civil War battlefields 
or Mount Rushmore, for example. 

■ Natural quiet is a central resource value to the park and its absence 
imperils the totality of the visitor experience, especially when the 



34 



4.8 Recommendation 8 



visitor comes to the park expecting peace and quiet and enjoyment 
of nature and natural sounds. For example, an experience in a 
canyon in southern Utah is not complete without the call of a canyon 
wren or the sounds of wind. An experience of the northern lakes is 
not complete without the call of loons. 

■ Wilderness has been designated on all or part of the park, and given 
characteristics of the terrain and sound attenuation, opportunities for 
solitude would be substantially diminished by overflights. This 
requires the area to be at least 5,000 acres in size unless there are 
special circumstances. 

In some cases these criteria could be used as the basis to petition the FAA to 
implement, through their rulemaking process, an aircraft management plan 
for that park to establish flight corridors or flight tracks that would keep 
areas naturally quiet and preserve the visitor experience of them. 

4.7 Recommendation 7 

Develop a Movie Waiver Policy 

The NPS recommends that FAA amend its policy relating to the conditions 
and limitations for movie filming operations conducted in national parks. 
The new policy should require the operator flying the filming crew to have 
the following: 

■ An operating plan specific to the park where the filming is being 
done. 

■ Approval of the plan by the park superintendent 

■ Notification of the appropriate Flight Standards District Office 
(FSDO) 

4.8 Recommendation 8 

Develop an Interagency Airspace Coordination Guide/Training 

The NPS recommends that the NPS, FAA, and the military services complete 
an Interagency Airspace Coordination Guide that would incorporate what 
the agencies learn about how to resolve airspace/park use conflicts. The NPS 
and the Air National Guard are currendy developing a proposal to DOD's 
Legacy Program for that purpose. It is further recommended that this be the 
basis for training interagency planners from all the agencies involved, pilots 
from the Armed Services, etc. 



35 



EXECUTIVE SUMMARY: Recommendations 



4.9 Recommendation 9 

Seek Continued Improvements in Safety and Interagency Planning 
Related to Airspace Management 

The NPS makes the following recommendations with respect to safety and 
planning: 

■ FAA and the NPS work together joindy to investigate the parks 
where serious safety issues may exist. FAA would take corrective 
actions if appropriate. 

■ FAA and NPS joindy develop a reporting format for safety issues to 
be used as part of interagency issue resolution processes. The NPS 
would use this format to report additional issues as they arise. 

■ Land management agencies, the FAA and the DOD need to give 
greater priority to identifying how to avoid collisions associated with 
the Temporary Flight Restrictions arotfnd forest fires. Department of 
Interior agencies need to support development and use of CAHIS 
(Computer-Aided Hazard Information System). 

■ Land management agencies, including the NPS, should provide the 
Armed Services with geographically-based databases of their noise 
sensitive areas for use in Armed Services planning. 

All the agencies need to explore how to get critical items highlighted in each 
others planning processes. 

4.10 Recommendation 10 



Improve SFAR 50-2 to Effect and Maintain the Substantial 
Restoration of Natural Quiet at Grand Canyon National Park 



Epilogue 

Achieving an equitable balance between the impacts and benefits of aviation 
in parks is a difficult but desirable task, one that is still in its infancy. It is a 
long-term goal for both the NPS and the FAA to seek that balance. Prior to 
the establishment of the Department of the Interior — Department of 
Transportation Interagency Working Group and the emerging dialogue 
between the FAA and the NPS, there was no adequate method to address the 
issue. The NPS is confident that with the FAA's continued cooperation and 
good faith that both agencies will be part of the balanced resolution of 
potential difficulties. It is a new way of doing business for both the NPS and 
the FAA and one that holds promise for the future. 



36 



tf&*f?f6 



l 



INTRODUCTION 

1 . 1 Background 

The National Park Service (NPS) was created by Congress to 

". . . promote and regulate the use of Federal areas known as 
national parks ... [so as to] conserve the scenery and the 
natural and historic objects and the wild life therein and to 
provide for the enjoyment of the same in such manner and by 
such means as will leave them unimpaired for the enjoyment of 
future generations. " 

In doing so, the NPS's mission was seemingly defined with an inherent 
conflict between the goal of conservation and the goal of providing for 
enjoyment. Enjoyment requires that visitors have access to the parks, and 
conservation requires that such access not damage or diminish the resources 
that the park was created to protect. But the NPS Organic Act was amended 
by the Redwoods Act of 1978, and this act unambiguously defines resource 
preservation as the primary responsibility for the Park Service. Given that 
natural quiet is a clearly identified resource, that aircraft overflights can 
disturb this resource and that the Federal Aviation Administration (FAA) 
controls use of the airspace, meshing the disparate missions of the NPS and 
FAA has, until recendy, appeared to be an intractable task. 

For three main reasons, aircraft flying low over parks present the NPS with a 
very different and unusual set of problems. 



/. NPS Organic Act, I6USC I 



39 



REPORT TO CONGRESS: Introduction 



First, the "natural quiet" found in many national park units has long been 
regarded as a park resource. This perspective is reflected in law, policy and 
by park visitors. It is a highly valued and increasingly rare resource in some 
parks that can be affected by low-flying aircraft. 

Second, the effects produced in parks by aviation are perhaps less obvious 
and, in some ways, less permanent than the effects produced by visitors on 
the ground. Worn trails and facilities, crowded camping areas and 
automotive traffic jamming park roads are easily observed and agreed upon 
effects that threaten visitor enjoyment. The overflight of a single aircraft, 
however, creates what is often perceived as a temporary visual effect, 
produces non-natural sound levels that are audible for a finite period, and 
may, if flying low enough and fast enough, startle visitors or the horses/mules 
of mounted visitors resulting in some risk of injury. Because of the paucity of 
studies and the difficulty of quantitatively proving impacts on visitors, 
wildlife, or other resources, the visual and audible effects produced by 
aircraft tend to be judged subjectively with the^acceptability of these effects 
being a matter of personal opinion (Dunholter, et. al. 1989) . 

The third main reason this is such an unusual and difficult problem is that 
the authority to legally exercise control on aviation access does not lie with 
the NPS. For all visitors to parks who travel by ground, the NPS has the 
authority to manage their impacts. Whatever type of ground transportation 
visitors use, the NPS can control where, when and how park areas are 
accessed and used. Further, any 

*. . . public accommodations, facilities, and services as have to 
be provided within those areas should be provided only under 
carefully controlled safeguards against unregulated and 
indiscriminate use, so that the heavy visitation will not unduly 
impair [park] values and so that development of such facilities 
can best be limited to locations where the least damage to park 
values will be caused. 

Thus, for access on ground, the NPS can exercise controls based on park 
policies developed to fulfill the mission of the NPS and of the specific park. 

On the other hand, Congress unambiguously vested authority for all aspects 
of airspace management in the Administrator of the FAA. The Federal 
Aviation Act of 1958 gives the Administrator the authority and the mandate 



2. While extensive research has been completed on the effects of aircraft overflights on urban populations in the vicinity of airports, [a 
literature search conducted for the National Park Service] revealed a shortage of information on the subjects qfenroute aircraft sound, 
aircraft sound in wilderness settings, or the acoustic effects on a park visitor population. 

3. Access via aviation means, for this report, aircraft flying over land areas administered by the NPS for use and enjoyment of park resources. 

4. 19 Stat. 969 



40 



] . 7 Background 



to prescribe rules and regulations governing the flight of aircraft, including 
rules as to the safe altitude of flight, for the purposes of 1) the navigation, 
protection, and identification of aircraft, 2) the protection of persons and 
property on the ground, 3) the efficient utilization of navigable airspace, and 
4) protection to the public health and welfare from aircraft noise and sonic 
boom. 

Thus, to the extent that use of airspace has effects on park lands, the NPS 
must work with the FAA to determine what controls are possible. Such a 
division of authority has meant in some cases that where NPS and FAA are 
unable to agree, resolution has had to occur through the President or 
Congress. 

This type of conflict resolution between resource protection and airspace use 
is not new. Aircraft flights over and into the area now designated as the 
Boundary Waters Canoe Area Wilderness present an early example. As early' 
as the 1930's, floatplanes provided sport fishing access to the Superior 
National Forest (now the Boundary Waters Canoe Area Wilderness) in 
northern Minnesota, and by 1 948 Ely, Minnesota was reputed to be the 
largest freshwater floatplane base on the continent with approximately 70 
planes making multiple round trips per day into remote lakes. Considerable 
publicity through writings and a short documentary film brought national 
attention, and on December 17, 1949, President Truman issued Executive 
Order 1 0092 establishing an airspace reservation of certain areas of the 
Superior National Forest. The order prohibited, with a few exceptions, flight 
below the altitude of 4,000 feet above Mean Sea Level (MSL) over 
designated areas. In 1978, Congress passed the Boundary Waters Canoe 
Area Wilderness Act into which E.O. 10092 was incorporated by reference 
(FAA, 1988). 

Grand Canyon National Park (GCNP) has had ever increasing overflights by 
aircraft. But whereas aircraft provided transportation to lakes in the Superior 
National Forest, aircraft use over Grand Canyon National Park is primarily 
for sightseeing purposes. Scenic tour flights began over the park in 1 926, 
when an airstrip was developed on the south rim near Red Butte. The 
completion the GCNP Airport in 1965, two miles south of the park 
boundary in Tusayan, contributed in a major way to the expansion of an air 
tour industry. By 1987, about 40 companies provided over 50,000 air tours 
over the canyon. 

The increasing number of flights over the Grand Canyon, combined with 
increases in air traffic over parks in Hawaii, the Colorado Plateau, and 
elsewhere raised both NPS and visitor concerns that overflights were having a 



5. S. Rep. No. 181 1, 85th Cong., 2d Sess. 14 (1958) 



41 



REPORT TO CONGRESS: Introduction 



significant impact on park values and on the visitor experience. For the 
Grand Canyon, this concern grew to such an extent that in January 1975, 
when Public Law 93-620, the Grand Canyon National Park Enlargement Act 
was passed, its Section 8 recognized "natural quiet" as a value or resource in 
its own right to be protected from significant adverse effect. In addition it 
specifically addressed the potential for aircraft or helicopter operations to 
cause a significant adverse effect on the natural quiet and experience of the 
park. 

Public Law 93-620 led to early research to determine if adverse effects were 
being caused by aircraft overflights. Acoustic research to develop a baseline 
on levels of aircraft sounds and sociological surveys to determine visitor 
reactions to the sound of aircraft were undertaken. Acoustic research found 
sound levels from aircraft to be quite high in various locations due to 
extensive numbers of flights. Surveys established that a range of visitors 
(from 20% of rim visitors, to 70% of backcountry users) were dissatisfied 
with aircraft overflights or related sound levels A Also in response to Section 8 
of the law, a public process was begun in October 1984 to review research 
and to discuss associated issues. By March of 1986, this process convinced 
the NPS that aircraft activity occurring over or within the park was causing a 
significant adverse effect on the natural quiet and experience of the park, and 
was likely to cause an injury to the health, welfare, or safety of visitors to the 
park. In June of 1986, two tour aircraft collided over the park, killing 25 
people. This tragedy focused national attention on the aircraft overflight 
issue at the Grand Canyon, and led in part to passage by Congress, in August 
1987, of Public Law 100-91, the National Parks Overflights Act. This report 
responds to the requirements of that law. 



1.2 Public Law 100-91 and this Report 

This law directed the NPS and the U.S. Forest Service to study the effects of 
aircraft overflights and report to Congress on the results. A less complex 
Forest Service study reported on work conducted earlier (USDA, 1992); this 
report presents the results of further studies conducted by the NPS. The law 
required that the NPS answer more complex and specific questions than the 
Forest Service. Table 1.1 lists these questions, the section of P.L. 100-91 in 
which they appear and the chapter or chapters that address each of the 
question areas. 



42 



1.3 Organization of Report 



TABLE 1.1 QUESTIONS POSED BY P.L. 100*91 


Question to be Answered 


Section of 
P.L. 100-91 where 
Question is Posed 


Chapters of Report 
that Address 
the Question 


1 . What is the nature and scope of the overflight problem in the 
National Park System? 


§l(b) 


2 


2. What are other injurious effects of overflights on the natural, 
historical, and cultural resources for which such units were 
established? 


§1 (c)(3) 


3,4,5 


3. a. What is the proper minimum altitude which should be 

maintained by aircraft when flying over units of the National 
Park System? 


§l(a) 


3 


b. What have been the effects of the minimum altitudes 
established over Yosemite and Haleakala National Parks? 


§2-(c) 


9 


c. Has the plan for management of airspace above the Grand 
Canyon succeeded in substantially restoring the natural quiet 
in the park? 


§3.(b)(3)(A) 


9 


d. What revisions in the airspace management plan for the Grand 
Canyon may be of interest? 


§3.(b)(3)(B) 


10 


4. What is the impairment of visitor enjoyment associated with flights 
over such units of the National Park System? 


§1 (c)(2) 


6 


5. What are the impacts of aircraft noise on the safety of the park 
system users, including hikers, rock-climbers, and boaters? 


§1 (c)(1) 


7 


6. What are the values associated with aircraft flights over such units of 
the National Park System in terms of visitor enjoyment, the protection 
of persons or property, search and rescue operations and firefighting? 


§1 (c)(4) 


8 



1.3 Organization of Report 

The organization of the report is based on the questions posed by Public Law 
1 00-9 1 . The nine major research areas of the report are described in this 
section: 

1 .3. 1 The Nature and Scope of Overflight Problems 

Chapter 2 presents information provided by park managers about the nature 
and scope of the problem. It examines which and how many parks are 
affected, what types of adverse effects or impacts are perceived, what types of 
aircraft and aircraft operations are responsible for overflights, how many 
overflights are estimated to occur, and how much of the time aircraft are 
audible at specific locations in eight national parks. 



43 



REPORT TO CONGRESS: Introduction 



1 .3.2 Effects of Overflights on Natural Quiet 

"Natural quiet" is a resource found in many parks which, under the NPS 
Organic Act, as amended, is to be protected. How and why overflights effect 
natural quiet in national parks is examined in Chapter 3. The chapter 
examines the importance of natural quiet, provides both qualitative and 
quantitative descriptions of natural quiet in parks, and discusses why natural 
quiet is so difficult to preserve. 

1 .3.3 Effects on Cultural and Historical Resources, Sacred Sites 
and Ceremonies 

The law requires information and evaluation of injurious effects of overflights 
on the historical and cultural resources of parks. Chapter 4 examines these 
effects from manager and visitor perspectives, and then discusses the 
potential for acoustic impacts and for vibration impacts. 

1.3.4 Effects on Wildlife 

Wildlife is one of the parks' natural resources that can be impacted by 
overflights, and is required to be examined by the law. Chapter 5 discusses 
physiological and behavioral responses of wildlife to overflights, presents a 
summary of observed responses for various species, and examines indirect 
effects of disturbance from overflights such as accidental injury, reproductive 
and energy losses and habitat avoidance and abandonment. It also presents 
factors that influence animal responses to aircraft, discusses some of the 
problems with detecting long-term effects of aircraft-produced disturbance, 
and examines the limitations of current information about wildlife responses 
to aircraft overflights. 

1 .3.5 Effects of Overflights on Visitors 

P.L. 100-91 directs the NPS to provide information and an evaluation of the 
impairment of visitor enjoyment associated with flights over units of the 
National Park System. Chapter 6 draws on information primarily from two 
different surveys of visitors to examine how aircraft overflights affect visitors 
and their enjoyment of the parks. Visitor opinions about overflights are 
presented both for the National Park System (excluding Alaska), and for 39 
specific parks. Visitor opinions addressed include ratings of how overflights 
affect their enjoyment, how overflight sounds rate as a problem compared 
with other sounds, types of aircraft heard, and effects of hearing or seeing 
aircraft. Visitor opinions are used to rank order the 39 parks by "degree of 
overflight problem", and this ranking is used to better understand visitor 
opinions and reactions. Management rankings of park overflight problems 
are compared with the visitor-based ranking. Finally, study results that 



44 



7.3 Organization of Report 



quantitatively relate visitor reactions (responses) to measured aircraft sound 
levels (doses) are presented. 

1 .3.6 Aircraft Overflights and Safety 

Chapter 7 presents management concerns about safety, with specific 
examples at surveyed parks, gives visitor opinions about aircraft and safety, 
and discusses the special problems associated with Temporary Flight 
Restrictions around forest fires or other major incidents. 

1 .3.7 Values Associated with Aircraft Overflights 

Public Law 1 00-9 1 also requires that the research provide information and 
an evaluation regarding "... the values associated with aircraft flights ... in 
terms of visitor enjoyment, the protection of persons or property, search and 
rescue operations and fire fighting." Chapter 8 examines these benefits from 
management and air tour passenger perspectives. 

1 .3.8 Restoration of Natural Quiet 

P.L. 100-91 explicidy states that "Noise associated with aircraft overflights at 
the Grand Canyon National Park is causing a significant adverse effect on the 
natural quiet and experience of the park. . . ." The Act requires the NPS to 
implement a plan for management of air traffic, and to report on 
". . . whether the plan has succeeded in substantially restoring the natural 
quiet in the park. ..." The Act also sets limitations on flight over Yosemite 
National Park and Haleakala National Park. Chapter 9 specifically examines 
the effectiveness of the minimum flight altitudes set in accordance with P.L. 
100-91 in Yosemite and Haleakala National Parks and addresses whether 
Special Federal Aviation Regulation (SFAR) 50-2, stemming from this 
legislation, has succeeded in substantially restoring natural quiet in the Grand 
Canyon National Park. 

1 .3.9 Conclusions, Issues and Recommendations 

Chapter 10 presents conclusions of NPS studies, issues needing to be 
addressed, and NPS recommendations. It also specifically addresses the P.L. 
100-91 question of whether possible revisions to SFAR 50-2 are necessary. 

1 .3. 1 Availability of NPS Studies 

The series of NPS studies upon which this report is based are listed in 
Appendix A and are available through the National Technical Information 
Service. 



45 



tf0*(^& 



2 



NATURE AND SCOPE OF OVERFLIGHT PROBLEMS 
IN THE NATIONAL PARK SYSTEM 



The effect of aircraft overflights on public lands has been a concern to land 
management agencies for many years. Beginning in the 1 940's with the 
floatplane access to the Boundary Waters Canoe Area Wilderness and 
sightseeing tours over the Grand Canyon in the late 1 960's, an established air 
tour industry has developed that provides tours over 30 — 40 national parks 
including such diverse areas as the Grand Canyon, the Hawaiian parks, the 
Badlands of South Dakota, Cape Cod National Seashore, and Great Smoky 
Mountains National Park. In addition, the need for military training space 
and the preference that this be located over unpopulated areas, as well as 
increasing long-distance commercial air travel mean that the airspace over 
public lands is under increasing demand. Public Law 100-91 recognized the 
increased concern about aircraft, and in directing the study of park 
overflights, gave specific requirements that the nature and scope of the 
problems be determined. Section 1(b) of the law states: 

The study shall identify any problems associated with overflight 
by aircraft of units of the National Park System and shall 
provide information regarding the types of overflight which may 
be impacting on park unit resources. The study shall distinguish 
between the impacts caused by sightseeing aircraft, military 
aircraft, commercial aviation, general aviation, and other forms 
of aircraft which affect such units. 

In response to this section, the NPS took three major actions: 



47 



REPORT TO CONGRESS: Noture and Scope of Overflight Problems in the National Park System 



First, in 1992 a list of parks affected by aircraft overflights was 
developed and a questionnaire mailed to each park manager. Detailed 
data were collected about the nature and extent of the problems. 
(McDonald et al. 1 994) This questionnaire asked about both factual 
matters and matters of opinion. Questions of fact addressed the use of 
aircraft by the park, the numbers and types of other aircraft that fly over 
the park, visitor complaints and safety issues. Questions of opinion, 
specifically to be answered by the park manager, asked about the general 
types of problems occurring in the park, the level of concern about 
various problems, the existence and significance of any problems created 
by aircraft overflights, and opinions about how any aircraft-related 
problems should be resolved. 

Second, a study to estimate the aircraft-produced sound exposure for all 
park units as well as USFS wildernesses areas was completed. 
(Tabachnick et al. 1 992) Since data on exposure were prohibitively 
expensive to collect for all parks, this efforjt to characterize the sound 
exposure for all parks used secondary information such as maps of the 
parks, maps of military and commercial aviation routes, and estimates of 
overflight operations. This report provides estimates of noise exposure 
for each NPS unit and for each Forest Service Wilderness, and permits 
a rank ordering of parks or wildernesses by "exposure". 

Third, four sound measurement studies were completed. (Dunholter et 
al. 1 989; Fidell eta/. 1994; Horonjeff et al. 1993; Miller et al. 1994) 
Each of these studies served a different purpose, and all but the first 
provide comparable quantitative data on aircraft and non-aircraft sound 
levels in various parks. First, the Mestre Greve report addressed the 
techniques for measuring aircraft sounds within park and wilderness 
settings and examined the acoustic parameters that are important in 
describing aircraft sound within such settings. Second, though the BBN 
study had several objectives, a primary one was to determine the extent 
to which natural quiet had been restored in the Grand Canyon; as part 
of this investigation, sound measurements were made in the Grand 
Canyon during the fall of 1989 and the spring of 1990. Third, the 
purpose of the first HMMH study was to measure and present detailed 
"acoustic profiles" for 23 locations in Grand Canyon National Park, 
four locations in Hawaii Volcanoes National Park, and four locations in 
Haleakala National Park. Fourth, the second HMMH study developed a 
simplified method for collecting sound level data, and park personnel 
were trained in the method and used it to collect data in five units of the 
National Park System: Cumberland Island National Monument, Glacier 



/. NPOA Report 92-1 provides in its Figure 5-3 the specific equations used to compute noise exposure. 



48 



2. 1 Survey of Park Managers 



National Park, Mount Rushmore National Memorial, Petroglyph 
National Monument, and Yosemite National Park. 

This chapter reports on the information provided as a result of these three 
specific actions. The information is combined and summarized to provide an 
overall picture of the numbers of park units affected, the aircraft overflight 
types and numbers, the degree of concern about the impacts of overflights, 
and the sound levels that result from these overflights. 



2.1 Survey of Park Managers 

The survey of park managers collected information about the numbers of 
park units experiencing aircraft overflight problems, the types of aircraft 
operations affecting each park, the types of impacts produced by the 
overflights, and additional detail about the park managers' perception of 
aircraft overflights and associated problems. 

2.1.1 Number of Parks Affected 

The survey first determined the number of park units affected by aircraft 
overflights. A screening telephone call to Regions and parks identified 98 out 
of the then-total of 34 1 non-Alaska parks as having some type or level of 
concern about overflights. Figure 2. 1 depicts the relationship between parks 
with identified overflight problems and those without. It shows this 
relationship in terms of numbers of parks, park acreage, and visits . Figure 

2.2 displays the 98 identified park locations, and Appendix B lists them. This 
leads to Conclusion 2.1 drawn in the sidebar. 



Extent of Aircraft Overflight Problems 






53% 



47% 



Number of Parks 
(341 units) 



Acreage 
(25,470,955.01 acres) 



Visitation 
(273,465,349 
recreation visits) 



□ Percent of NPS Units not Reporting Overflight Concern 
EHU Percent of NPS Units Reporting Overflight Concern 



Figure 2. J: Extent of Aircraft Overflight Problems in the National Park System 



CONCLUSION 2.1: 

NPS managers believe that 
approximately 30% of all 
National Park System units 
have aircraft overflight 
problems. These affected parks 
account for about three-fourths 
of the total NPS administered 
acreage, and about half the 
total park visits. Low-level 
overflights constitute a 
management problem for the 
NPS, one that needs to be 
addressed in a systematic 
manner. 



2. Visils are defined as the number of people entering a park over the course of the year Jor recreational purposes. 



49 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the Notional Park System 



v 



.84 



> <-- 26 

^35 

,** 70 ; 

/ ) WASHINGTON. 



I 



L 
82 



OREGON 37 
27 



7 \ 

I IDAHO 
28 



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J 



NORTH 
DAKOTA 



/ S»/^ 
MINNESOTA „ Z- C~, 



■\ 



| 48 



31 SOUTH DAKOTA 

i 69 s 



! i 



WISCONSIN 89 ; 






MAINE > 



f NEW YORK ', 

-i- 



MICHIGAN 

\ : PENNSYLVANIA^ ^34 



;£f* 



-»47 


9d\ 






UTAH 


( 






61 \ 








i COLORADO 


\ 


\ 


v 


/ 97 


11 


10 




\CALIFC 


\ 


^ — ._ 


.... 81 










30N" 


i 46 
- 49 


72~" 


■i...J>7_ 


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^ 






77 


14 
95 


19 






2tf\ 


58 ) 


ARIZONA 


6 


39 






/ 






NEW MEXIC< 




\\2 








j 






"-{^ 






96 
44 


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i 








-75 


85 ; 


93 


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- 51 



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...■..--,::3 38«. 



40 DC 



/w 



N. y KENTUCKY 

i.-.J 65 .._ 



'"'wv /-'e8^%^ MD 

83;'V 
, VIRGINIA 24> 



'" ~7 NORTH 



OKLAHOMA : ARKANSAS Jv 

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MS 



LOUISIANA \ 



CAROLINA 

TENNESSEE , / 30 . 

<- ' '*" .'SOUTH V/ 

21 CAROLINA / 
i 60 »- 25 / 

\ 32> 
ALABAMA; GEORGIA 






18\ 



29 



vv 



13\ 

XFIOKID* 



59, 



54^ 
/80 N 



*5 



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VIRGIN 
ISLANDS 



Figure 2.2: Locations of the 98 Park Units with Identified Aircraft Overflight Problems 



CONCLUSION 2.2: 

Managers report that 

overflights of parks result from 

all types of aircraft; general 

aviation and military aircraft 

overflights are the types most 

often mentioned. This reporting 

of overflights of many aircraft 

types reinforces the notion that 

a systematic approach is 

needed to address these issues 

and to identify the most serious 

overflight problems. 



2. 1 .2 Types of Aircraft Overflights 

The survey asked park managers to identify the types of aircraft flying over 
their parks. Figure 2.3 shows the number of parks with overflight problems 
that mentioned each of four general types of aircraft overflights. Parks 
identifying each of these types of overflights included: general aviation- (8 1), 
military (78), high-altitude commercial (55), and sightseeing (42). 

2. 1 .3 Types of Impacts 

The survey also asked managers to identify the types of impacts they believed 
the aircraft overflights produced at their parks. In general, the types ot 
impacts may be characterized as safety related, sound related and visual 
related. 

One question on the survey asked "Do you feel visitors are concerned for 
their safety as a result of aircraft overflights over your park?" Eighteen NPS 
managers perceived overflights to be a serious or very serious safety issue for 
their park. 



50 



2. 1 Survey of Park Managers 



A second question asked managers to identify, from a list of sources of 
sounds, which types of sound they considered a problem, and also to identify 
the degree of the problem. Eighty-eight of 9 1 responding parks identified 
the sounds from "airplanes, jets, helicopters or any other aircraft" as a 
problem to some degree. 

A third question asked managers to identify the extent to which aircraft 
activity adversely impacts visitors, using a five scale choice from "no impact" 
to "very large impact". Sixty-four of 88 responding parks said that aircraft 
overflights had some degree of impact on the "ability of visitors to appreciate 
park scenery." These responses are graphed in Figure 2.4 as a "visual" 
impact. 



Types of Aircraft Overflights 

for 88 Parks Reporting Overflights 



100 



80 



£ 60 



40 



20 





7.8 










55 








;;:$xj: : :;;;x;:;;:$:vx:;>';:;>:0! 




- 






81 




42 













Military 



Sightseeing Commercial General Aviation 



CONCLUSION 2.3: 

NPS managers most often 
identified the sound of aircraft 
overflights as producing 
negative impacts on visitors. 
Safety was judged as least 
frequently impacted. Reported 
visual impacts, though perhaps 
highly dependent on the scenic 
resource, upon the way in 
which the question was asked 
(or on the person answering the 
survey), were nevertheless not 
as commonly judged as 
negative. 



Figure 2.3: Types of Aircraft Overflying National Parks as Identified by Managers 



100 



80- 



£ 60 

o 



■a 

| 40 

2 

20 + 



Types of Aircraft Overflight Impacts 

for Parks Reporting Overflights 









88 




















64 










■ i 




27 




■" 











Safety 



Sound 



Visual 



Figure 2.4: Park Manager Judgements of Types of Impacts 



Not all porks responded to specific questions on the survey. 



51 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the National Park System 



2. 1 .4 Estimated Numbers of Overflights 



The survey asked managers to estimate the numbers of overflights per week 
that their parks experienced. They were asked to make these estimates for 
six types of operations: 1) military training, 2) sightseeing tours, 3) 
transporting commercial passengers between cities, 4) park management, 
research and maintenance, 5) emergency services like fire fighting or search 
and rescue, and 6) private aircraft flights (general aviation). The numbers 
used here are intended by the reporting parks to include all overflights in 
order to provide a sense for relative numbers of overflights, and to show the 
nature and potential scope of the overflight problem. 

Figure 2.5 sums the number of overflights per week reported by the surveyed 
parks to provide an indication of the relative level of operations. The total 
indicates that commercial operations are apparendy responsible for the 
greatest number of overflights. Even if the estimates for George Washington 
Memorial Parkway (6,300 commercial overflights), Golden Gate National 
Recreation Area (14,000 commercial overflights), Joshua Tree National Park 
(7,000 overflights) and Manassas National Batdefield Park (3,200 
overflights) are removed, the results still show (Figure 2.6) that commercial 
overflights are judged to generate more than twice as many overflights as 
either sightseeing or general aviation. Military overflights and park 
management and emergency operations are, respectively, the least common 
types of overflights. 



-Q 

E 



Estimates of Overflights per Week 

Summed Across 88 Reporting Parks 



40,000 



j= 30,000- 



if 20,000-- 



10,000- 



11 



!:!;'■!: 



wmm 



Military 



Sight- Commercial Manage- Emergency General 
seeing menl Aviation 



Figure 2.5: Reported Number of Overflights per Week by Aircraft Type for All Parks 



52 



Estimates of Overflights per Week 

Without 4 Parks Near Busy Airports 



14,000 

12,000 

10,000 

8,000 

6,000 

4,000 

2,000 





Military Sight- Commercial Manage- Emergency General 

seeing menl Aviation 



Figure 2.6: Reported Number of Overflights per Week Reduced by Four Parks 



2. 1 Survey of Park Managers 



Estimates of overflights are presented in alternative form in Figures 2.7 
through 2.1 1. The figures group parks by numbers of reported overflights 
per day. (Overflights per day are computed by dividing reported overflights 
per week by seven.) Each figure presents the distribution of parks for a 
different type of aircraft operation. Figure 2.7 shows the distribution of the 
9 1 reporting parks for all operations. 

(For example, 36 parks reported that the number of overflights for all types 
of operations as between 1 and 10 per day. Similarly, 10 parks reported 
fewer than 1 overflight per day and 19 parks reported having between 10 and 
50 overflights per day). 

Figures 2.8 through 2.11 provide the distribution for the four types of 
operations: military, sightseeing, commercial, and general aviation. These 
data suggest several generalizations. First, though many of the parks 
experience military overflights (78 parks, see Figure 2.3), most of the parks 
report relatively few military overflights per day (fewer than 1 per day, 
Figure 2.8). Alternatively, though a smaller number of parks report 
sightseeing overflights (42 parks, Figure 2.3), those that do tend to report 
greater numbers (up to 50 per day or more, Figure 2.9). Commercial and 
general aviation distributions tend to lie between these two patterns: more 
parks report commercial overflights than report sightseeing, and numbers 
range from modest to very high (over 500 per day, Figure 2. 10). More parks 
report experiencing general aviation overflights than report any other type 
(8 1 parks, Figure 2.3), but most report fewer than ten overflights per day 
(Figure 2. 11). 



CONCLUSION 2.4: 

Reported numbers of overflights 
by type of operation vary 
considerably from park to park. 
Relatively few parks receive 
high numbers of any one type 
of overflight. Commercial and 
sightseeing operations are 
more prevalent than other types 
of overflights. Military and park 
administrative overflights are 
least common. 



53 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the National Park System 



50 



40 ■■ 



£ 30-- 



-Q 

E 



20- 



10- 



Distribution of All Overflights 

Based on Management Estimates 



Ml 






— ai 



Unknown <1 1<10 10<50 50<100 100<500 500 + 



Figure 2. 7: Distribution of Overflights per Day for All Aircraft Combined 



Distribution of Military Overflights 

Based on Management Estimates 



50 



40- 



£ 30- 



20-- 



10-- 



! ■ : --m tmmm mmam 



Unknown <1 1<10 10<50 50<100 100<500 500+ 



Figure 2.8: Distribution of Overflights per Day for Military Aircraft 



Distribution of Sightseeing Overflights 

Based on Management Estimates 



50 



40 



£ 30 



E 20 

2 

10 



t - ' M 



Unknown < 1 1<10 10<50 50<100 100<500 500 + 



Figure 2.9: Distribution of Overflights per Day for Sightseeing Aircraft 



54 



Distribution of Commercial Overflights 

Based on Management Estimates 



50 



40 
30 + 
20 
10 + 



: : >:'x> : ::-:-: : :--: 

■ ¥:¥:¥:■: 

<m ■■: 

:-: : :v:-: : :-:-: : x 



.. 



' f'""' M, "1 



Unknown <1 1<10 10<50 50< 100 100<500 500+ 



F/gure 2. 10: Distribution of Overflights per Day for Commercial Aircraft 



Distribution of GA Aircraft Overflights 

Based on Management Estimates 



50 



40 



30 •■ 



-o 
| 20 



10- 



0-" 



■ ■'■y'y-y-y- " ' 



I 

mm 



Unknown 



<1 1 < 1 10<50 50<100 100<500 500 + 



Figure 2.11: Distribution of Overflights per Day for General Aviation Aircraft 



2. 1 .5 Superintendents' Judgments of Overflight Problems 

The survey specifically asked NPS managers their opinions about several 
matters related to aircraft overflights. The questions attempted to determine 
the overall level of concern superintendents have about overflights and the 
types of effects they believe overflights produce. Most questions were to be 
answered with a five-point scale ranging from "no concern" or "not a 
problem" to "extremely concerned" or "very serious problem". 



2. ) Survey of Park Managers 



55 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the National Park System 



CONCLUSION 2.6: 

Most, though not all, managers 

of the parks with perceived 

overflight problems rate aircraft 

as one of their most important 

problems. Also, managers 

demonstrate differing degrees 

of concern about overflights. 

Hence any systematic method 

for assessing aircraft overflight 

problems should be designed to 

incorporate local management 

objectives in the identification 

of the problem and in 

developing solutions. 



CONCLUSION 2.7: 

The starting point for resolving 

overflight issues over national 

parks needs to begin with an 

examination of those parks 

whose managers are very to 

extremely concerned about 

overflights. 



Degree of Concern 

Each manager was asked to judge the seriousness of ten specific types of 
potential problems in his/her park. Figure 2.12 shows how many 
superintendents reported each of the problems to be a moderate, serious or 
very serious problem. For example, 53 responded that mechanical noises like 
vehicles, aircraft and generators were either a moderate, serious or very 
serious problem. Only maintenance of park facilities and damage to natural 
resources were rated as problems by more superintendents. Additionally, 
managers were asked to rate six different specific sounds as potential 
problems, and Figure 2.13 summarizes the responses. Of the 91 reporting 
superintendents, 65 (over 70 percent) rated the sounds from airplanes, jets, 
helicopters and any other aircraft to be a moderate, serious or very serious 
problem. The next most often identified sound-related problem was road 
traffic, with 37 parks (about 40 percent) rating cars, buses, trucks or 
motorcycles as a moderate to very serious problem. 

The managers were also asked to identify their overall concern about aircraft 
activity over the park. Figure 2.14 gives the distribution of their responses. 
Overall, 67 out of 9 1 who answered this question responded that they were 
either moderately, very or extremely concerned about aircraft activity. The 
parks whose managers are very or extremely concerned about aircraft 
overflights are listed in Table 2.1. 



TABLE 2.1 NATIONAL PARKS WHOSE MANAGERS ARE VERY TO EXTREMELY 


CONCERNED ABOUT AIRCRAFT OVERFLIGHTS 


EXTREMELY CONCERNED 


VERY CONCERNED 


Bandelier National Monument 


Big Cypress National Preserve 


Cape Lookout National Seashore 


Bryce Canyon National Park 


City of Rocks National Reserve 


Channel Islands National Park 


Fort Vancouver National Historic Site 


Crater Lake National Park 


Glacier National Park 


Guadalupe Mountains National Park 


Great Smoky Mountains NP 


Joshua Tree National Park 


Haleakala National Park 


Kalaupapa National Historical Park 


Hawaii Volcanoes National Park 


Lassen Volcanic National Park 


Isle Royale National Park 


Manassas National Battlefield Park 


Kings Canyon & Sequoia NP 


Mesa Verde National Park 


Minute Man National Historic Park 


Mount Rainier National Park 


Organ Pipe Cactus Nat. Monument 


Navajo National Monument 


Shenandoah National Park 


Perry's Victory & Int. Peace Memorial 


Southern Utah Group 


Statue of Liberty National Monument 




Prince William Forest Park 




Pu'uhonua o Honaunau NHP 




Puukohola Heiau National Historic Site 




Saguaro National Monument 




San Antonio Missions NHP 




White Sands National Monument 



The Southern Utah Group (Canjonlands National Park, Arches National Park, and Natural Bridges National Monument) was inadvenendy left out of 
the Survey but has requested that it be shown here. 



56 



2. J Survey of Park Managers 



Managers' Rating of Potential Problems 

(91 Parks w/Overflight Problems) 




Maintenance of Facilities 

Damage to Plants, etc. 

Mechanical Noises 

Development Outside the Park 

Damage to Artifacts, etc. 

Quality of Services 

Air, Water Pollution 

Availabiity of Facilities 

Number of Visitors 

Dev. Inside Park 


H64 









; ""' """ 154 


Hi 53 


J51 




1150 


| 44 


il| 44 : 




: ' - J41 




137 




116 


( 


) 10 20 30 40 50 60 7 
Number of Porks 



Figure 2. 12: Managers' Rating of Ten Potential Problems in Their Parks 



Managers' Rating off Sound Problems 

(91 Parks w/Overflight Problems) 



Aircraft 

Road Traffic Vehicles 

Power Generators 

Audio Equipment 

Domestic Animals 

People Talking 




10 20 30 40 50 60 
Number of Parks 



70 



Figure 2. J 3: Managers' Rating of Sound-Related Problems in Their Parks 

Types of Effects 

NPS managers were asked to give their judgments about specific effects of 
aircraft overflights. First they were asked, if they had concerns about aircraft 
overflights, what bothered them most about the aircraft activity. Figure 2.15 
shows how many park managers rated any of six effects as moderate, serious 
or very serious problems. Most managers (69 out of 9 1 responding parks) 
believed the loudness was a problem, while the particular areas overflown 
was next most often identified. Fewest managers considered aircraft to be a 
threat to visitor or staff safety. 



57 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the National Park System 



-o 

E 



Managers' Concern about Overflights 

(91 Parks w/Overflight Problems) 



50 



40 ■■ 



i 30 ■■ 



20- 



10-- 




Not at all Slightly Moderately Very Extremely 



CONCLUSION 2.8: 

Loudness and area overflown 

were the most bothersome 

aspects of overflights to NFS 

managers. With respect to 

impacts on visitors, managers 

were most concerned about the 

ability of the visitors to 

experience natural quiet and 

the sounds of nature, although 

other noise impacts were 

identified. An understanding of 

the -specific park problem will 

be important to factor into any 

systematic approach to 

resolving or mitigating 

overflight issues. 



Figure 2.14: Managers' Reported Degree of Overall Concern about Overflights 

NPS managers were also asked to rate five possible impacts on visitors, and 
Figure 2.16 summarizes the responses. Figure 2.16 shows the number of 
managers who responded that they rated the impact on the listed qualities as 
moderate, large or very large. The largest number (63) responded that 
overflights produced impact on the "ability of visitors to experience natural 
quiet and the sounds of nature." Forty- three thought aircraft produce 
moderate to very large impact on the "ability of visitors tq appreciate the 
historical and/or cultural significance of the park." About equal numbers of 
managers identified impact on the ability of visitors to "hear interpretive 
programs," or "appreciate park scenery," or to "carry on normal 
conversations." 



2.2 Estimates of Overflight Exposure 

Development of a logical and rigorous plan for conducting field studies of 
aircraft overflights required estimates of aircraft overflight exposure for all 
units of the National Park System and for Forest Service Wildernesses 
(Tabachnick et al. 1992). Exposure estimates permit a rank-ordering to 
insure that all levels of exposure were studied. But the limits of cost and 
schedule prevented collection of on-site acoustic data or direct observation 
of overflights, and considerable effort was devoted to collection of 
information through secondary sources. Maps and charts were used to locate 
parks and wildernesses. Aeronautical charts used by general, commercial and 
military aviation planning and routing provided location information for 
various routes and flight areas. The FAA tried to provide information on use 
of high altitude jet routes for four seasons, but at the time of the report had 



58 



2.2 Estimates of Overflight Exposure 



Managers' Rating of Overflight Effects 

(91 Parks w/Overf light Problems) 



Loudness of Some Flights 

Areas Overflown 

Number of Plones 

Duration of sound 

When Aircraft Fly 

Safety of Visitors or Staff 



'■■:'■ 


■/-:--:<-l.-y-':''':-:'<<-:^y---'': 
















64 


■'■'■ ' ■'■ '" '"■■■'■'' . ■ ■ ■ " ' " : ■ " ■■ . ■ ■ " ■' 








37 

54 


'W:''\';- : \MMi< 








llllltliii; 










. . .. ' ■■ 


46 






34 : 




1 1 3= 



69 



10 



20 30 40 50 

Number of Porks 



60 



70 



Figure 2. ?5: Managers' Rating of Most Bothersome Aspects of Overflights 



Managers' Rating of Overflight Impacts 

(91 Parks w/Overflight Problems) 



Natural Quiet 

Historical Significance 

Interpretive Programs 

Park Scenery 

Normal Conversation 





63 








43 ; 




















33 ; 






1 


31 

o 












3 


10 


20 


30 


40 


50 


60 


7( 



Number of Parks 



Figure 2. 16: Managers' Rating of Overflight Impacts on Visitors' Enjoyment 



only been able to provide partial information. Despite a formal 
Memorandum of Understanding between the Secretaries of Defense, 
Agriculture, and Interior, it was not possible to obtain information suitable 
for inclusion in this effort from the Department of Defense. Telephone 
interviews of tour operators, used to ascertain flight activity on sightseeing 
routes, yielded some information, but several operators refused to provide 
information or referred inquiries to national or state coalitions of air tour 
operators. Finally, there is no accurate method for estimating the level of 
general aviation traffic on any route within any airspace. Furthermore, there 
is no strong correlation of exposure based on these numbers and the 
numbers of visitors who reported hearing aircraft, or the number of 



CONCLUSION 2.9: 

It is extremely difficult, if not 
impossible, to obtain accurate 
determinations of aircraft 
activity over units of the 
National Park System without 
on-site collection of objective 
information. Moreover, 
numbers of overflights by 
themselves are not necessarily 
indicative of the extent of 
exposure to aircraft sounds or 
of the severity of a sound 
exposure problem. 



59 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the National Park System 



overflights reported by the NPS managers or with the degree of concern 
expressed by managers. 



2.3 Sound Measurement Results 

There are many methods for collecting objective data on-site that can be 
used to quantify aircraft activity over units of the National Park System. One 
method is to measure aircraft sound levels, and various types of sound 
measurements have been conducted in many of the national parks over the 
years. In response to Public Law 100-91, the NPS conducted four sound 
measurement studies, and three of these provide sound measurement results 
that can be readily compared and summarized. 

Percent of Time Audible 

Though many metrics are available for quantifying sound, one that the NPS 
has found has proven useful in examining the sounds produced by aircraft 
overflights of national parks is the "percent of time audible". NPS studies 
found this metric to be best correlated with visitors' response to sound (see 
Chapter 6 and Anderson et al. 1993). This is a measure of the amount of 
time aircraft can be heard at a specific location by an attentive listener, and it 
is simply the percent of the time that the listener can hear aircraft. It is a 
measure that is very easy to compile with no special instrumentation other 
than a stop watch, a pencil and a sheet of paper. As will be discussed in 
Chapter 6, "Effects on Visitor Enjoyment," percent of time audible is useful 
because it can be related to visitor reactions to the sound of aircraft 
overflights. It is also useful because it accounts for the non-aircraft sound 
levels. For example, if a site is near flowing water or a parking area, the 
aircraft may not be heard as easily as in a very quiet location. Hence, percent 
of time audible is a measure of how long aircraft sound levels protrude above 
all other sounds. As will be discussed in Chapter 6, percent of time audible is 
easy to measure but extremely difficult, to compute or predict. Hence, once a 
problem site is identified with percent of time audible data, data collection 
and analysis need to be done with an analytically manageable metric (e.g. 
Equivalent Level or Leq). 

Figure 2.17 summarizes the percent of time aircraft were audible at specific 
locations in eight units of the National Park System. 

Grand Canyon: Data were collected in Grand Canyon National Park 
during three time periods, including shoulder (Spring and Fall) and high 
visitor use seasons. The first two data collection efforts, in October/ 
November of 1989 and in April/May of 1990, were conducted by observers 
who made continuous digital sound level tape recordings, and who pressed a 



60 



2.3 Sound Measurement Results 



button that recorded a tone on the tape whenever an aircraft was heard. 
(Fidell et al. 1994) The 1989 and 1990 data were collected at each of the 
locations listed in Figure 2.17 for periods of several hours per day for four or 
more days. In general, the average time for data collection at these 1989 and 
1 990 sites was 1 6 hours. Thus, for example, at Sanup Plateau, where data 
were collected a total of about 24 hours, aircraft could be heard for about 14 
hours or 58 percent of the time. 

The third period of data collection occurred between August/September of 
1992, and data was acquired by observers who used sound level monitors 
that collected and stored sound level data once a second, and who used 
palm-top computers to key in the times aircraft were heard, the type of 
aircraft, and the type of non-aircraft sounds that could be heard when no 
aircraft were present. Data were collected for about 4 hours at each location, 
except at four sites where visitors were also interviewed (see Chapter 6). At 
the four interview sites, sound level data were collected an average of 1 5 
hours. All data were collected during daylight hours. 

Though these measurements provide far more data than is displayed in 
Figure 2.17 (see the following section "decibel based data"), the percent of 
time audible metric provides a means for a simple and quick comparison of 
the extent to which aircraft are audible. Parts 1 and 2 show aircraft audibility 
in various parts of the Grand Canyon. For the sites measured, aircraft were 
heard from a low of about 5 percent of the time to a high of almost 80 
percent of the time. The sites were not randomly chosen, so should not be 
thought of as representing all possible aircraft sound exposures in the 
Canyon. Rather, the data should be taken to show the general range of 
aircraft sound exposures and to show that there are many locations where 
aircraft could be heard for moderate to high percentages of the time. 

Hawaiian Parks: The techniques used in 1992 in the Grand Canyon were 
also applied in Hawaii. (Horonjeff et al. 1993) Data were taken over 4 to 6 
hour periods at four of the sites (Kalahaku Overlook, Pu'u Mamane, Pu'u 
O'o and Halemaumau Crater) and for periods of 2 1 to 25 hours at the other 
four locations. The results are presented in part 3 of Figure 2.17. 

Five Other Parks: Park personnel were trained in the use of a simplified 
method to collect sound level data. The method requires a sound level meter 
and limited training in use of a specialized data form (Miller et al. 1994). It 
yields several sound metrics, including percent of time aircraft are audible. In 
general, the method requires that sound level samples be taken every 1 5 
seconds for 20 to 30 minute periods with the observer keeping a log of 
which samples include audible aircraft sound. The method was used by park 
personnel in the five parks shown in Figure 2.17, parts 3 and 4. 



CONCLUSION 2.10: 

"Percent of time audible" 
provides a simple method for 
the NFS to use in quantifying 
how much of the time aircraft 
can be heard at locations in a 
given national park. 



61 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the National Park System 



Sound Measurement Summary — 1 

Locations in Eight National Paries 




GRAND CANYON — 1989 

Sanup Plateau . 

Horn Canyon . 

Hermit Creek . 

Tuna Creek ■ 

Dona Butte ■ 

Tuweep Overlook ■ 

Cope Butte ■ 

Pinal Point • 

Phantom Ranch ■ 

GRAND CANYON — 1 990 

Hermit Creek ■ 

Sanup Plateau ■ 

Point Imperial ' 

Horn Canyon ' 

Desert View ' 

South Canyon 

Nankoweap ' 










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) 10 20 30 40 50 60 70 80 90 100 
Percent of Time Aircraft Audible 



Sound Measurement Summary — 2 

Locations in Eight National Parks 



GRAND CANYON — 1 992 

Hermit Basin 
Point Sublime 
Point Imperial 
Toroweap Overlook 
96 Mile Camp 
Burnt Springs Canyon 
Little Colorado River 
Lipan Point 
Desert View 
Whitmore Rapids 
Bright Angel Point ■ 
Separation Canyon ■ 
Phantom Ranch Overlook (Edge) ■ 
Diomond Creek 
Marble Canyon (Mile 35.2 ■ j5» T^2 
Havasu Creek . 
Yaki Point . x7£ 
Phantom Ranch Overlook . 
Deer Creek Falls (Across River) . WZj 
Marble Canyon/Buck Farm Canyon . !?x5l 
Deer Creek Falls (1/2 Mile NE) . ^ 
Stone Creek Camp . «£] 
1 17.4 Mile Camp . ST 




100 



Percent of Time Aircraft Audible 



Figure 2. 1 7: Sound Measurement Results Acquired in Eight National Parks 



62 



2.3 Sound Measurement Results 



Sound Measurement Summary — 3 

Locations in Eight National Parks 






HALEAKALA — 1 992 

Kolahaku Overlook' 

Pu'u Mamane' 

Sliding Sands (Bottom)- 

Sliding Sands (Top) ' 

HAWAII VOLCANOES — 1 992 

1 mi. West of Pu'u Co- 

Wahaula Temple (Temple) ■ 

Wahaula Temple (Rood) ■ 

Halemaumau Crater' 

CUMBERLAND ISLAND — 1993 

South Cut Trail' 

Sea Camp Campground ■ 

Willow Pond Trail & Beach ■ 

Trail — Yankee CG & Hickory Hill • 

MOUNT RUSHMORE — 1993 

Borglum View Terrace ■ 

Main View Terrace ■ 

Middle Marker- 

YOSEMITE — 1 993 

Rafferty Creek ■ 

Sodo Springs ■ 

Mirror Lake Road ■ 

Glacier Point ■ 









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10 20 30 40 50 60 70 80 90 
Percent of Time Aircraft Audible 


K 



Sound Measurement Summary — 4 

Locations in Eight National Parks 






PETROGLYPH — 1993 

North Geologic Window ■ 

81 St. Addition . 

Volcanoes Pkg. Lot ■ 

Bond Volcano - 

Piedras Marodas ■ 

Airfield Proximity ■ 

Rinconada ■ 

Mesa Top Trail Top ■ 

Paseo Del Norte - 

Inner Piedras Morados ■ 

Laurelwood - 

Rinconada VC ■ 

Alcove ■ 

Boca Negra Canyon ■ 

Meso Top above Taylor Ranch ■ 

Rock 1 -2-3 ■ 

Homestead Cir. Dr. ■ 

Highview Dr. ■ 

Mid Piedras Moradas Canyon - 

Lava Shadows VC • 

Losimagines VC • 

GLACIER — 1993 

Logan Pass - 

Middle Fork ■ 






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Percent of Time Aircraft Audible 



63 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the Notional Park System 



CONCLUSION 2.11: 

"Percent of time audible" data 

taken in eight national park 

units, though limited for some 

of these areas, suggests that 

there are locations and times in 

many of these parks where 

aircraft can be heard for 

significant portions of time. 



Cumberland Island: Measurements were conducted eight times at 
the four locations, so that each site was monitored for about 4 hours. 
Thus, for example, out ot about 4 hours of listening at the Sea Camp 
Campground, aircraft could be heard more than 55 percent of the time. 

Mount Rushmore: Measurements were conducted more than 20 
times over nearly two weeks time at the three sites, and each site was 
measured for eight to ten hours total. Hence, over approximately 10 
hours of monitoring at Borglum View Terrace, aircraft could be heard 
more than 40 percent of the time. 

Yosemite: Measurements were conducted twelve times over one to 
three days at the four sites for a total measurement time of about six 
hours at each site. Thus, out of 6 hours of listening, aircraft were 
audible more than half the time at three of the four locations: Rafferty 
Creek, Soda Springs and Mirror Lake Road. 

Petroglyph: Measurements were conducted for approximately 20 
minutes at each location. Thus, measurements here provide information 
over more locations, but with less certainty at any single location. The 
results in Figure 2.17, part 4, show the wide variation in aircraft sound 
that can be experienced in this park. Of 2 1 locations where 
measurements were made, aircraft could be heard more than half the 
twenty minute listening period at 1 5 sites. 

Glacier: Measurements were conducted seven times over three days at 
Logan Pass, and three times over two days at Middle Fork. This small 
sample is not believed to be representative of the situation in Glacier. Of 
iVi hours of listening at Logan Pass, for example, aircraft could be 
heard slightly more than 1 percent of the time. 

Sound Level Data 

Report NPOA 93-4 presents detailed sound level data collected in 1992 in 
the Grand Canyon and in Haleakala and Hawaii Volcanoes National Parks. 
Figures 2.18 and 2. 19 present samples of these "acoustic profile" data 
measured in the Grand Canyon and in the Hawaiian Islands, respectively. 
The form is a graphic one (though the data are also tabulated in NPOA 
93-4), and shows both non-aircraft background levels, and maximum aircralt 
produced levels for the entire day's measurement, a period of 4 to 7 hours 
for the locations shown. 



64 



2.3 Sound Measurement Results 



The vertical axis of the graph shows the A-weighted sound level in decibels. 
The curve on the left-hand portion of the graph describes the background 
sound level; the " + " signs on the right hand side describe the maximum 
sound levels of individual aircraft overflights. The curve on the left shows 
how background levels varied over the measurement. At Separation Canyon 
(site number 9, see Figure 9.2 in Chapter 9), background levels were 
between approximately 3 1 dB and 1 2 dB; ten percent of the time they were 
above 26 dB and 90 percent of the time they were above roughly 16 dB. In 
comparison, the aircraft that were measured produced maximum levels, 
Lmax, between about 28 and 57 dB. When the aircraft levels are about the 
same as the background levels, at least for some of the time, aircraft sounds 
will tend to be less audible or "masked"; aircraft levels that are above all 
background levels are easily heard. 

Separation Canyon is in an area where the minimum flight altitude is 5000 
feet above sea level (MSL). The elevation of the site is about 1 300 MSL, so 
aircraft should be a minimum of 3700 feet above the site. Bright Angel 
Point, on the other hand, is well within a flight-free zone created by SFAR 
50-2 (See Chapter 9, Figure 9.1) and is one of the quietest areas with 
respect to aircraft sound. As shown, at Bright Angel Point many of the 
aircraft produced levels are at the level of the background sound levels, at 
least part of the time. Tour aircraft are audible less of the time at Bright 
Angel Point (about 6 percent of the time) than at Separation Canyon (about 
16 percent of the time, see Chapter 9, Tables 9.2 and 9.3). 

Toroweap Overlook is within, but at the edge of another SFAR 50-2 
flight-free zone. Aircraft stay over a mile from this location. The figure shows 
clearly, however, that aircraft sound levels considerably exceed the 
background levels, which are quite low. Point Sublime is also within a 
flight-free zone, and though aircraft levels are lower than at Toroweap, 
aircraft are audible more than 70 percent of the time. 

The data from the Hawaiian parks, Figure 2.19, suggest the effectiveness of 
setting minimum altitude restrictions. Over Haleakala (Sliding Sands and 
Kalahaku Overlook), P.L. 100-91 restricts flight to 9,500 MSL or higher; 
this restriction is intended to keep aircraft above the rim where the elevation 
is about 9,600 MSL. Both the Sliding Sands and Kalahaku sites are at about 
9,400 MSL. On the other hand, there are no altitude restrictions for 
Wahaula Temple or Pu'u O'o. Some aircraft flew quite low over Wahaula 
Temple. 



CONCLUSION 2.12: 

Flight-free zones can be 
designed to effectively limit 
aircraft sound levels, but they 
must be very large if natural 
quiet is to be restored or 
substantially restored. 



65 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the Notional Park System 



90 



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Measured 
Values of 

l-max f° r 
Aircraft 
Events 



10 20 30 40 50 60 70 80 90 100 

Percent of Time Background Level on Vertical 
Scale is Exceeded 



SEPARATION CANYON (9) 



90 



80 - 



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50 - 



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Measured 
Values of 

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Aircraft 
Events 



10 20 30 40 50 60 70 80 90 100 

Percent of Time Background Level on Vertical 
Scale is Exceeded 



BRIGHT ANGEL POINT ( 1 0) 
Figure 2. 1 8: Acoustic Profile Data from Grand Canyon National Park 



66 



2.3 Sound Measurement Results 



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BACKGROUND 




AIRCRAFT 



Measured 

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Aircraft 

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10 20 30 40 50 60 70 80 90 100 



Percent of Time Background Level on Vertical 
Scale is Exceeded 



TOROWEAP OVERLOOK (14) 



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Percent of Time Background Level on Vertical 
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PO/NTS(JBL/ME(J9) 



67 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the National Park System 






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10 20 30 40 50 60 70 80 90 100 

Percent of Time Background Level on Vertical 
Scale is Exceeded 



SLIDING SANDS — BOTTOM (52) 



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10 20 30 40 50 60 70 80 90 100 



Percent of Time Background Level on Vertical 
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KALAHAKU OVERLOOK (55) 
Figure 2. 1 9: Acoustic Profile Data from Haleakala and Hawaii Volcanoes Nafional Parks 



68 



2.3 Sound Measurement Results 



80 



BACKGROUND 




'■'■'■' 



^AIRCRAFT 



Values of 

i-max f° r 
Aircraft 
Events 



10 20 30 40 50 60 70 80 90 100 



Percent of Time Background Level on Vertical 
Scale is Exceeded 



WAHAULA TEMPLE — TEMPLE (63) 



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10 20 30 40 50 60 70 80 90 100 

Percent of Time Background Level on Vertical 
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PU'U O'O (65) 



69 



REPORT TO CONGRESS: Nature and Scope of Overflight Problems in the National Park System 



CONCLUSION 2.13: 

Minimum altitude restrictions 

can help limit aircraft sound 

levels, but the restrictions 

should be carefully chosen, 

considering location and 

elevation of the park areas of 

concern. 



2.4 Summary 

It is likely that there could be as many as 50 to 1 00 units of the park system 
where overflight problems are likely or certain to exist. NPS managers have 
consistently, for nearly a decade, identified 30-40 parks as priorities for 
research and problem solving. NPS managers believe about 30 percent or 
approximately 100 of the National Park System units (excluding Alaska) 
experience some level or type of aircraft overflights that constitute a 
problem. In one-third of this set of parks, managers are very or extremely 
concerned about overflights. More than half of the affected parks are 
overflown by military, commercial passenger aircraft and general aviation 
aircraft. Somewhat fewer are overflown by sightseeing aircraft. The primary 
impact of these overflights is believed by park managers to be the sound 
produced, and that the sound impact produced by aircraft is more of a 
problem than sound from any other sources. 

Because of the variations in numbers and types of overflights, a systematic 
method is needed to objectively determine the degree of the overflight 
problem. However, such a method must be integrated with management 
objectives. Park managers differ in their concern about aircraft overflights. 
Local conditions and management objectives play an important role in 
determining management concern. One objective method that can be used is 
measurement of "percent of time audible" which answers the question of 
how often aircraft can be heard. Sound level data in decibels, of the type 
presented in Section 2.3, graphically show the relation of aircraft to 
background sound levels. 



70 



tffaf^ 



3 



EFFECTS OF OVERFLIGHTS ON NATURAL QUIET 



The National Park Service manages "natural quiet" as a park resource. This 
responsibility is based in current public law, in explicit park management 
policy, and in visitors' reactions to park experiences. Just as parks contain 
many tangible features, such as animals, plants, waters, geological features, 
historic buildings and archeological sites, they have intangible qualities as 
well. These qualities include solitude, space, scenery, clear night skies, 
sounds of nature and 'natural quiet. Such qualities are increasingly rare in 
much of America. The scarcity of these resources and their importance to 
the park experience also makes diem valued by park visitors. 



3.1 How Important is Natural Quiet? 

The concept of natural quiet and its importance as a resource is embodied in 
the 1916 NPS Organic Act, as amended. For Grand Canyon National Park 
(GCNP), Congress embedded the concept into two major public laws. It is 
also stated quite explicidy in NPS policy. Natural quiet is also very important 
to park managers and to a majority of park visitors. 



/. NPS Organic Act, I6U.S.C. I 



71 



REPORT TO CONGRESS: Effects of Overflights on Natural Quiet 



3. 1 . 1 Importance to the Congress 

As directed by the Organic Act: 

* . . . The service thus established shall promote and regulate 
the use of the Federal areas known as national parks, 
monuments, and reservations hereinafter specified, except such 
as are under the jurisdiction of the Secretary of the Army, as 
provided by law, by such means and measures as conform to 
the fundamental purpose of such parks, monuments, and 
reservations, which purpose is to conserve the scenery and the 
national and historic objects and the wild life therein and to 
provide for the enjoyment of the same in such manner and by 
such means as will leave them unimpaired for the enjoyment of 
future generations. " 

The national parks must be managed to conserve their resources and allow 
their enjoyment. This section has been interpreted by the courts as providing 
the Secretary of the Interior with authority to determine how best to control 
these areas. 

The United States Congress has repeatedly recognized the need to preserve 
the national parks in their natural state. In Section 101 (b) of the Act of 
March 27, 1978, PL. 95-250 (The Redwood Act), 92 Stat. 166 (codified at 
16 U.S.C. 1), Congress stated that: 

". . . . The authorization of activities shall be construed and the 
protection, management, and administration of these areas 
shall be conducted in light of the high public value and integrity 
of the National Park System and shall not be exercised in 
derogation of the values and purposes for which these various 
areas have been established, except as may have been or shall 
be directly and specifically provided by Congress. " 

According to the legislative history of this provision, "the Secretary has an 
absolute duty, which is not to be compromised, to fulfill the mandate of the 
1916 Act to take whatever actions and seek whatever relief as will safeguard 
the units of the National Park System." Furthermore, 16 U.S.C. 3 indicates 
that to carry out these Congressional mandates, the Secretary of die Interior 
"shall make and publish such rules and regulations as he may deem necessary 
and proper for the use and management of parks. . . ." No limitations on the 
Secretary's power are noted. In the absence of specific Congressional 
mandate, the Secretary must determine for the National Park Service how 
best to protect park resources and thus how best to manage any adverse 
impacts. 

In the case of GCNP, Congress has provided direct and explicit guidance. In 
the Grand Canyon National Park Enlargement Act of January, 1975, 



72 



3. 1 How Important is Natural Qo/et? 



Congress stressed the importance of natural quiet in directing certain 
corrective actions whenever: 

". . . the Secretary has reason to believe that any aircraft or 
helicopter activity or operation may be occurring . . . which is 
likely to cause an injury to the health, welfare, or safety of 
visitors to the park or to cause a significant adverse effect on 
the natural quiet and experience of the park ..." (emphasis 
added) 

Twelve years later, Congress reiterated the same concern in Public Law 
100-91, The National Parks Overflights Act of 1987. A portion of that act 
states: 

"Noise associated with aircraft overflights at the Grand Canyon 
National Park is causing a significant adverse effect on the 
natural quiet and experience of the park and current aircraft 
operations at the Grand Canyon National Park have raised 
serious concerns regarding public safety, including concerns 
regarding the safety of park users. " 

Regarding guidance to achieve natural quiet in areas exposed to aircraft 
overflights, the legislative history of Public Law 100-91 provides important 
guidance on how a substantial restoration of natural quiet is to be achieved: 

"Plight-free zones are to be large areas where visitors can 
experience the park essentially free from aircraft sound 
intrusions, and where the sound from aircraft traveling adjacent 
to the flight-free zone is not detectable from most locations 
within the zone. " 



3. 1 .2 Importance of Natural Quiet to the National Park Service 

NPS management policy clearly articulates the value of natural quiet as a 
resource. Regarding the intrinsic value of the resource, NPS management 
policy (NPS 1988) states: 

The natural resources and values that the Park Service protects 
. . . include plants, animals, water, air, soils, topographic 
features, geologic features, paleontological resources, and 
aesthetic values, such as scenic vistas, natural quiet, and clear 
night skies ..." (emphasis added) 

NPS policy also tasks the agency with protecting natural quiet as a resource. 
Regarding protective actions to be taken, NPS policy (NPS 1988) states: 



2. Public Law 93-620, "Grand Canyon National Park Enlargement Act", 93rd Congress of the United States, January, 1975. 

3. Public Law 1 00-9 1 , "Aircraft Overflights Act", 1 00th Congress of the United States, August, 1987. 



73 



REPORT TO CONGRESS: Effects of Overflights on Natural Quiet 



'The National Park Service will strive to preserve the natural 
quiet and the natural sounds associated with the physical and 
biological resources of the parks (for example, the sounds of 
the wind in the trees or of the waves breaking on the shore, the 
howl of the wolf, or the call of the loon). Activities causing 
excessive or unnecessary unnatural sounds in and adjacent to 
parks, including low-altitude aircraft overflights, will be 
monitored, and action will be taken to prevent or minimize 
unnatural sounds that adversely affect park resources or values 
or visitors' enjoyment of them." (Emphasis added) 

These policy statements make clear the importance of natural quiet as a 
resource in many units of the National Park System. This resource is defined 
as the natural ambient sound conditions found in those units. It refers to the 
absence of mechanical noise, but accepts the "self-noise" of park visitors. 
This definition provides local park managers with a point of departure for 
developing strategies to protect this resource. 

NPS-77, Natural Resource Management Guidejines (NPS 1990), also 
addresses the issue of protecting aesthetic values. The Guidelines define 
"aesthetic value" as a: 

". . . value, in the framework of natural resource management 
in the NPS, that is attributed by people to natural, 
unmanipulated conditions and is perceived through the senses 
— by seeing, hearing, touching, smelling, and tasting." 

The Guidelines provide guidance on considering basic questions of aesthetics. 

"To determine whether a proposed action or activity may affect 
resources and values important to the aesthetic experience, 
consideration of the following questions may be helpful. The 
questions can assist not only in evaluating the activities and 
actions that take place outside park boundaries, but also in 
those under the regulatory control of the NPS within park 
boundaries. . . 

Could the action or activity be seen from the park. . . ? 

Could the action or activity be heard in the park? Where in the 
park would the sound be most noticeable or intrusive? From 
developed overlooks, headquarters areas, or trails? Would the 
sounds be continuous or intermittent? Are there any ways in 
which the effects of the sound could be mitigated or 
lessened. . . ? 

Would the perceptible sight or sound change the nature or 
quality of the visitor's experience? In what ways. . . ? 



4. "Self-Noise" is the noise generated by the visitor — the tread of hiking boots on the trail, the creaking packframe, ratde of pots or pans, talking, etc. 



74 



3. J How Important is Natural Quiet? 



Does the frequency or duration of the activity or action affect 
the degree to which it could be perceived? 

As these questions indicate, systematically looking at the effects of proposed 
activities or actions aims at evaluating what may be lost. . . 

The Guidelines further note that the courts have been reluctant to expand 
the regulatory control of the Service for aesthetics beyond designated park 
boundaries. NPS managers are encouraged to look for methods other than 
litigation or Congressional appropriations to preserve the aesthetic integrity 
of parks. 

3. 1 .3 Importance of Natural Quiet to Park Managers 

In 1992 the NPS surveyed the managers of 98 parks (excluding Alaska parks) 
who had reported overflight problems. Although the questionnaire solicited 
the opinions about many aspects of aircraft overflights, three of the questions 
asked managers to consider the issue of natural quiet. As applied to their 
particular park, these questions asked for opinions about: 

The importance managers ascribe to providing an opportunity for park 
visitors to appreciate the natural quiet of the park, 

The degree to which managers feel aircraft activity interferes with their 
ability to provide this opportunity, and 

The degree to which managers feel aircraft activity negatively impacts 
visitors' ability to appreciate natural quiet. 

Figure 3.1 provides a summary of the responses to the first question. 
Although managers attached most importance to visitor enjoyment at most 
parks, the opportunity for natural quiet is extremely important to half the 
managers, and moderately to very important to roughly the other half. 
Figure 3.2 shows the responses to the second question. More managers 
believe aircraft overflights interfere with the opportunity for natural quiet, 
and to a greater degree, than believe aircraft interfere with enjoyment or 
historical significance. (These views, that aircraft most interfere with natural 
quiet, are confirmed by visitor surveys, see Section 3. 1 .4 and Chapters 6 
and 9.) 



5. This question was asked in a context of three different opportunities: Visitor Enjoyment, Appreciation of Natural Quiet, and Appreciation of Historical 
Significance. 

6. This question was asked in a context of Jive potential impacts: Normal Conversation, Natural Quiet, Historical Significance, Park Scenery; and Hear 
Interpretive Programs. 



75 



REPORT TO CONGRESS: Effects of Overflights on Natural Quiet 



Importance of Opportunity 

(Manager's Survey) 




Enjoyment Natural Quiet Historical Significance 

^B Moderately ^^ Very Much I I Extremely EI551 TOTAL 



Figure 3. 1 : Importance to Management of Various Opportunities 



Interference with Opportunity 

(Manager's Survey) 



100 




Enjoyment Natural Quiet Historical Significance 

^m Moderately ^H Very Much I I Extremely r&m TOTAL 



Figure 3.2: Management Perspective on Interference with Opportunities 



CONCLUSION 3.1: 

Preserving natural quiet is an 

integral part of the mission of 

the NPS. This is confirmed in 

law, policy, and the beliefs of 

NPS managers. Aircraft are 

judged by most managers to 

interfere with this opportunity, 

and interfere more with this 

opportunity than with other 

types of opportunities. The 

specific mandates and 

opportunities of individual 

parks to provide natural quiet 

need to be considered when 

estimating the severity of the 

effects of overflights. 



As part of the third question, managers were also asked to rate the degree to 
which aircraft activity impacted four aspects of the visitors' experience 
besides natural quiet. Those additional aspects were normal voice 
conversation, historical significance of the park, enjoyment of the scenery, 
and the ability to hear interpretive programs. Figure 3.3 shows the managers' 
responses and puts the issue of natural quiet in perspective with these 
additional concerns. The length of each bar in the figure shows the 
percentage of managers who rated impact to be moderate to extreme for 
each aspect of the experience. In comparison with other potential impacts, 
natural quiet drew the highest percentage of responses. 



76 



3. 1 How Important is Natural Quiet? 



3.1 .4 Importance of Natural Quiet to Park Visitors 

A survey of visitors to the Grand Canyon (Baumgartner et al. 1994) showed 
how different visitor groups felt impact from aircraft overflights. Figure 3.4 
provides information about five different Grand Canyon visitor groups: 
frontcountry visitors, summer and fall backcountry visitors, river users in 
motorized boats, and river users in oar-powered boats. For all groups, more 
visitors reported impact in terms of interference with natural quiet, than 
reported interference with enjoyment or annoyance. 

Figure 3.4 shows also that overflights of the Grand Canyon produce greater 
impacts, in terms of percent of visitors who are affected, in the backcountry 
than in the frontcountry. Though the reasons for this greater impact cannot 
be determined, it is evident that backcountry use (including river use) does 
not provide an escape from the impacts of overflights. 



CONCLUSION 3.2: 

Aircraft appear more likely to 
interfere with natural quiet for 
visitors than with visitor 
enjoyment or to produce 
annoyance. This relationship 
held true for Grand Canyon 
visitors, regardless of activity. 



Negative Impact of Aircraft Activity 

(Manager's Survey) 



100 
90 
80 
70 
60 
50 
40 
30 
20 
10 








■ 




















:-: ; : : : : x : : : : : : : :: : : : : ::: : : : : >: : : : : : 












1 
11111111 
















;v,J 



Natural Quiet Historical Hear 

Significance Interpretive 
Programs 



Scenery Conversation 



Figure 3.3: Management Reports of Aircraft Impact on Park Resources 



Visitor Reports of Impacts 

By Type of Visitor Activity 




Frontcountry Summer Fall River: Motor River: Oar 

Backcountry Backcountry 



I Interference with Enjoyment 



] Annoyed t::::xi Interference with Natural Quiet 



Figure 3.4: Grand Canyon Visitor Reports of Aircraft Impact on Park Resources 



77 



REPORT TO CONGRESS: Effects of Overflights on Natural Quiet 



3.2 What is Natural Quiet? 

Parks and wildernesses offer a variety of unique, pristine sounds not found in 
most urban or suburban environments. They also offer a complete absence 
of sounds that are found in such environments. Together, these two 
conditions provide a very special dimension to a park experience. 

In considering any sound environment, it is often helpful to classify the 
components of the environment into one of two categories: those sounds 
that contribute to the more or less continuous background (ambient) sound 
environment (such as waves breaking on the shore, or a distant waterfall), 
and those sounds which are intermittent in nature (such as the call of a 
coyote, or the passing of a flock of vocal geese). This distinction is important, 
because it is the ambient environment that establishes the quieter moments 
in the park, and provides masking to intermittent sources (such as aircraft). 

3.2. 1 Qualitative Assessment of Natural Quiet 

Quiet itself, in the absence of any discernible source (especially man-made), 
is an important element of the feeling of solitude. Quiet also affords visitors 
an opportunity to hear faint or very distant sounds (such as animal activity, 
waterfalls, etc.). Such an experience provides an important perspective on 
the vastness of the environment in which the visitor is located, often beyond 
the visual boundaries determined by trees, terrain, and the like. 

The range in ambient sound levels, even from indigenous sources, can vary 
considerably from one location to another, or time to time at any given 
location. At one end of the spectrum is the sound level at the base of a 
powerful waterfall. At the other end of the spectrum is the near absence of 
any perceptible sound at all. These latter conditions may be found in areas 
devoid of flora or fauna. In the middle is an array of sound conditions which 
vary from moment to moment, hour to hour. During non-inclement weather 
conditions, these variations result from three factors in natural environments: 

■ Wind (its interaction with foliage, irregular terrain, or the human ear) 

■ Water (movement in steams, falls, or wave action) 

■ Animal (near continuous, such as insect; or intermittent, such as 
birds, coyotes, etc.) 

Lulls in the wind or interludes between animal sounds create intervals where 
the quiet of a sylvan setting is quite striking. In considering natural quiet as a 
resource, the ability to hear clearly the delicate and quieter intermittent 
sounds of nature, the ability to experience interludes of extreme quiet for 
their own sake, and the opportunity to do so for extended periods of time is 
what natural quiet is all about. 



78 



3.2 Whot is Natural Quid? 



3.2.2 Quantitative Assessment of Natural Quiet 

To provide a quantitative perspective on the quiet found in many parks, 
Figure 3.5 shows sound levels for a range of park and non-park settings in 
the form of an "acoustic thermometer." Values at the bottom of the 
thermometer are very quiet. In comparison, values at the top of the 
thermometer are much noisier. The sound levels shown on the thermometer 
are measured in decibels. 



Sound Level Ranges for Some Park 
and Non-Park Settings 

A-Weighted Sound Level (decibels) 

80 Typical Outdoor Setting 

Noisy Urban (daytime) 
70 

Commercial Retail Area NON-PARK 
60 

Suburban (daytime) 
50 

Suburban (nighttime) 

40 

I Grand Canyon (along river) 
30 

Hawaii Volcanoes (crater overlook) 
20 

Grand Canyon (remote trail) PAOif 

10 ■ ■• 

Haleakala (in crater, no wind) 




Figure 3.5: Sound Level Ranges Between Park and Non-Park Settings 

The "A-weighted sound level" tide over the scale refers to an internationally 

recognized measurement standard that accounts for the different sensitivity 

of the human ear to different frequencies (pitches) of sound. This standard is 

used to assure that two different sounds which seem equally loud to a human 

7 
observer will have very nearly the same measured sound level, in decibels . 

The thermometer in Figure 3.5 is divided into two ranges. The upper half 
shows sound levels of typical non-park settings, and the lower half shows the 
ranges of sound levels measured in. parks. At the high end of the non-park 
environments are outdoor settings in downtown areas of large, busy cities, 
such as New York, Chicago, or Washington, DC. Further down the scale are 
daytime suburban settings out-of-doors in areas around these cities, and 
even further down are out-of-doors suburban settings at night. 

In the lower range are sound level environments found in parks. This range 
includes sound levels that most people who live in urban or suburban 
environments rarely encounter during their normal daily routines. At the 
upper end of this range are areas along a major river, such as the Colorado 



7. Technically, the specified ranges of Figure 3. 5 may he thought of as identifying commonly occurring equivalent levels, L et ,,for the identified location and 
condition. 



79 



REPORT TO CONGRESS: Effects of Overflights on Natural Quiet 



CONCLUSION 3.3: 

The quiet afforded in park 

settings is virtually in a range of 

its own, well below that which 

we experience in our normal 

daily routine. 



River in GCNP. In the middle of the range are scenic overlook areas where a 
few visitors may congregate at any one time, and areas along remote 
backcountry trails where encounters with other visitors are infrequent. 

At the very bottom of the range are extremely quiet areas of parks or 
wildernesses generally devoid of vegetation or major terrain features which 
might generate noise from the wind or might support insect or animal 
populations. In the absence of wind, these locations have ambient levels very 
near the human threshold of hearing. Such environments may be found in 
places like Death Valley National Monument or in the crater of Haleakala 
National Park (where they have been measured with specialized 
instrumentation). To put the lower half of the figure in some perspective, 
sound levels in the 20 to 30 decibel range would be found late at night inside 
a single family residence, with all windows closed, no internal noise sources 
operating (such as heating or ventilating systems) and no local traffic in the 
vicinity. 

Some perspective on how quiet the natural environment of a park can be 
may be gained by comparing the two ranges in Figure 3.5. The relatively 
large sound level range (of roughly 40 decibels) that can be found between a 
busy downtown area and the suburbs at night, can also be found in park 
areas, but lying entirely below the lowest of the common outdoor sound 
levels in suburban environments. In such quiet park areas, it is not surprising 
that even relatively quiet aircraft can be heard at great distances. 



3.3 What Are the Characteristics of Natural Quiet? 

Generally low sound levels, but with considerable variability over both time 
and location, characterize the ambient sound environments in many national 
parks. The rise and fall of the wind in a coniferous forest can change the 
ambient sound level over a matter of minutes at a single location. Likewise, 
the synchronized activity of insects such as crickets can produce substantial 
changes in the ambient sound environment as well. 

From one location to the next, the proximity of vegetation and water, the 
local insect population (and its normal diurnal activity patterns), and the 
location's susceptibility to winds can give rise to large differences in ambient 
sound levels. Figures 3.6 through 3.8 show a range of ambient sound levels 
measured during the summer and fall of 1992 at a number of diverse 
locations in three parks. (Horonjeff et al. 1993) The bars in each figure show 
the range in sound levels observed 90 percent of the time during the 
measurements (5 percent of the time levels were higher than shown, and 5 
percent of the time levels were lower than shown). 



80 



3.2 What is Natural Quiet? 



Ambient Sound Level Ranges 

Grand Canyon National Park — River 



Havosu Creek 

Marble Canyon (mile 35.2) 

Stone Creek Camp - 

Deer Creek Falls (Across River) 

1 17.4 Mile Camp 

Phantom Ranch Overlook (Edge) 

96 Mile Camp 

Whitmore Rapids 

Little Colorado River 

Phantom Ranch Overlook 

Deer Creek Falls (1/2 mile) 

Diamond Creek 

Marble Canyon / Buck Farm Conyon 

Burnt Springs Canyon 

Separation Canyon 







10 20 30 40 50 

A-Weighted Sound Level (decibels) 



60 



Figure 3.6: Measured Ambient Sound Levels Along Colorado River in 
Grand Canyon National Park 



Ambient Sound Level Ranges 

Grand Canyon National Park — Rim 



Desert View 

Yaki Point 

Li pan Point 

Point Imperial 

Bright Angel Point ■ 

Hermit Basin 

Toroweap Overlook - 

Point Sublime 



■ : r" 

■i ;-■ 

■ — : ■ 

* r* 

■ — i ■ 

■ : -■ 



o 



10 20 30 40 50 

A-Weighted Sound Level (decibels) 



60 



Figure 3. 7: Measured Ambient Sound Levels Along the Canyon Rim in 
Grand Canyon National Park 



Ambient Sound Level Ranges 

Hawaiian Parks 




HAWAII VOLCANOES — 1 992 

Wahaula Temple (Temple) - 

Halemaumau Crater - 

Wahaula temple (Troilhead) - 

1 mi. West of Pu'u O'o - 

HALEAKALA — 1992 

Kalohaku Overlook - 

Sliding sands Trail (Top of Crater) . 

Pu'u Mamane . 

Sliding Sands (3/4-Mile into Crater) . 




i 








* 






























< 


) 10 20 30 40 50 6 

A-Weighted Sound Level (decibels) 


3 



Figure 3.8: Measured Ambient Sound Levels in Hawaii Volcanoes and 
Haleakala National Paries 



81 



REPORT TO CONGRESS: Effects of Overflights on Natural Quiet 



Looking at the three figures as a whole, a range of almost 50 decibels may be 
observed between the levels at Havasu Creek on the Colorado River and the 
lowest levels along Sliding Sands Trail in the crater of Haleakala National 
Park. Such a range is indicative of the differences to be found across the 
remote visitation areas of the park system. Within a single park the range can 
be almost as large. Generally speaking, at locations dominated by water 
noise, the range in ambient levels will usually be smaller (the 2 to 1 decibel 
ranges, as shown in Figure 3.6) than in other areas due to the consistency of 
water flow. In other areas the range is generally 1 5 to 20 decibels (Figures 
3.7 and 3.8). 

The relationship between these quiet settings and aircraft overflights is 
shown in Figure 3.9. The vertical axis of this figure shows the sound level in 
decibels, and the horizontal axis shows the passage of time over a 50 minute 
period. In the upper left portion of the figure, a 20-minute portion of a 
sound level trace obtained at the Great Meadows National Wildlife Refuge is 
presented. Great Meadows is located in a suburban area approximately 25 
miles northwest of Boston, MA. The trace shows an ambient environment of 
45 to 50 decibels, largely controlled by wind interacting with deciduous 

Sound Level Time History 

Comparison of Two Noise Environments 



80 



70 ■--• 



60 - 



50-- 




j> 40 -- 



30 - 



20 



10 - 



Single Engine Piston Aircraft 



Great Meadows National 
Wildlife Refuge 
24 Aug 1992 



Commercial Jet 




10 



H 1 h 

20 30 

Time (minutes) 



40 



50 



Figure 3.9: Protrusion of Aircraft Noise Above the Ambient in Various Settings 



82 



3.4 Why is it Difficult to Preserve Natural Quiet? 



woods and distant road traffic. The trace also shows four single-engine 
propeller aircraft overflights which protrude 20 to 25 decibels above the 
ambient level, and are clearly audible in the ambient of Great Meadows. 

To the right in the figure is a 30-minute trace showing helicopter and 
ambient sound levels at Haleakala National Park. The extreme quiet of the 
crater is exemplified by the ambient sound levels ranging from 7 to 27 
decibels. The distant air tour helicopter at the beginning of the trace rises 
about 20 decibels above the ambient, and is clearly audible. The maximum 
level of this helicopter overflight is almost 10 decibels below the ambient at 
Great Meadows. Thus, the same helicopter overflight at Great Meadows 
would have been largely inaudible in that ambient environment. 

Later in the Haleakala trace, a commercial jet aircraft overflew the crater and 
the maximum level exceeded the ambient by approximately SO decibels. 
This event would have been noticeable in the Great Meadows environment 
as well as at Haleakala, but the protrusion of the sound event above the 
ambient is more pronounced at Haleakala, and is likely to be perceived as a 
greater intrusion. Immediately following the commercial aircraft overflight, a 
second air tour helicopter entered the crater area and began circling 
approximately one mile away. The maximum levels were about 30 decibels 
above the ambient and the aircraft was clearly audible. The same helicopter 
event in the presence of the Great Meadows ambient noise would have likely 
gone unnoticed. 

Another important observation to be made from Figure 3.9 is the dynamics 
of the ambient sound level. While the difference between maximum and 
minimum ambient levels is different for the two environments shown, for 
each ambient the sound level consistendy returns to within 2 or 3 decibels of 
the lowest levels every few minutes. Hence, in the absence of any other 
sounds, the visitor has a consistendy recurring opportunity to experience and 
appreciate the quietest levels the particular location has to offer. 



CONCLUSION 3.4: 

Extremely low ambient sound 
levels in many parks means that 
visitors to remote sections of 
those parks are likely to hear 
aircraft, even if aircraft sound 
levels are very low. 



3.4 Why is it Difficult to Preserve Natural Quiet? 

There are four primary reasons why natural quiet is difficult to preserve: 

■ Pressures to increase aircraft activity are on the rise in many parks 
(see discussions in chapter 8), and the NPS has no authority or 
influence over this activity. 

■ The quiet to be preserved is the lower end of the ambient sound 
level range that occurs regularly between wind gusts, animal sounds, 
etc., not just the average sound level. 



83 



REPORT TO CONGRESS: Effects of Overflights on Natural Quiet 



CONCLUSION 3.5: 

Preserving natural quiet is 

difficult because many park 

areas experience very low levels 

of ambient sound and aircraft 

are consequently audible at 

considerable distances (several 

miles). 



■ To provide a reasonable assurance that an aircraft will not be noticed 
by park visitors, the aircraft sound level cannot exceed the lowest 
levels of the ambient by more than a few decibels. 

The extreme quiet in many parks coupled with typical tour and commercial 
aircraft source levels require very large distances between the aircraft and the 
visitors to prevent audibility. (Anderson, G.S. et al. 1992) 

With aircraft activity on the rise in many parks and without FAA assistance in 
regulating the increases, the amount of uninterrupted time available for 
visitors to notice, appreciate and contemplate the quiet of the park will 
decrease proportionately. While more flights do not necessarily mean higher 
sound levels, there are two inevitable outcomes of increased flights. First, if 
increasing numbers of flights are routed along a limited number of existing 
flight corridors, then the length or number of quiet interludes between 
flights will decrease. If additional flight corridors are opened to serve the 
rising demand, then new land areas will be affected and interludes of natural 
quiet will be reduced in new (and perhaps previously unaffected) areas as 
well. 

With the exception of water-related sources, there are few naturally 
occurring sound sources in many parks which continually generate sound 
levels capable of masking the sound of nearby aircraft. Sources that do 
provide a predictable and constant level of masking sound generally do so to 
a fairly localized geographic area. High ambient levels from ocean surf, or 
from river rapids are usually limited to distances well under a mile, and 
therefore are of limited value in protecting large areas of a park from aircraft 
audibility. 



3.5 Aircraft Overflight Effects on Natural Quiet 

When visitors can hear the sound of aircraft, they cannot experience natural 
quiet. Specific areas within specific parks provide the opportunity to 
experience natural quiet. Such areas, however, are likely to have very low 
ambient sound levels and hence, intruding sounds will be more easily heard. 
For these areas, actions are necessary to preserve the natural quiet resource. 
The NPS recognizes that achieving natural quiet will not always be possible at 
these locations. There are locations where intruding sounds cannot be 
eliminated. Local street traffic, other visitor-generated mechanical noises as 
well as aircraft can eliminate natural quiet. On the other hand, studies have 
shown that visitor judgment of the importance of natural quiet varies, 
probably as a function of the type of visitor activity, (see Figure 3.4), and 
hence, from the visitor perspective, natural quiet is not equally important in 
all locations or for all visitor activities. 



84 



3.6 Summary 



In developing an approach to preserve natural quiet, the NPS recognizes the 
following five important facts: 

1 . Natural quiet is a resource for preservation within the NPS 
mandate. 

2. The human auditory system is an excellent mechanism for 
determining the presence or absence of natural quiet. No readily 
available electronic device can duplicate human hearing for 
identifying audible sounds produced by non-natural sources. 

3. The difficulty of preserving natural quiet is direcdy related to how 
quiet it is. If natural quiet, natural ambient sound, is relatively 
loud, as along a beach with pounding surf, or near a waterfall, 
then intruding non-natural sounds will have to be comparably 
loud to be heard. On the other hand, in a remote park location 
with no wind or water, or one with little or no vegetation or 
wildlife, even very quiet intruding non-natural sounds will be 
audible. 

4. Humans are not always aware of sounds that are audible. 
Humans, when engaged in any number of activities, may have 
their attention focused on the activity and not be aware that a 
new sound has become audible. Visitors who for the first time 
view the Grand Canyon at Lipan Point are not very likely to 
remember hearing any aircraft. Only about 30 percent of the 
visitors interviewed reported hearing aircraft, (see Chapter 6) 
even though roughly 90 percent of them could have. 

5. Park settings can provide levels of natural quiet so quiet that there 
is no sound to be heard except that generated by the listener — 
the sounds of walking, breathing, heart pumping, and blood 
flowing, (Figures 3.5 through 3.9). 



3.6 Summary 

The NPS studies discussed in this chapter demonstrate that: 

A natural sound environment, and especially the extreme quiet found in 
many parks, is a resource valued by both park management and visitors. 

The very low sound levels in many parks allow non-indigenous sounds, 
such as aircraft, to be clearly audible even at great distances, 



85 



REPORT TO CONGRESS: Effects of Overflights on Natural Quiet 



The complexity of the issue strongly suggests that a system-wide 
framework is required with flexibility to define unique park problems 
and solutions because it would: 

1 . carefully consider the resource values to be preserved and the 
types of experiences desirable to provide visitors, as well as 
consider the interests of the locally affected parties, and 

2. recognize both the visitation opportunities and variable visitor 
sensitivities in concert with the physical characteristics unique to 
each park location. 



86 



tf/r*f?f6 



4 



EFFECTS ON CULTURAL AND HISTORIC 
RESOURCES, SACRED SITES, AND CEREMONIES 

A variety of laws, executive orders, and regulations clearly charge the NPS 
with preserving cultural resources and providing for their enjoyment "in such 
manner and by such means as will leave them unimpaired for the enjoyment 
of future generations." Parks offer special opportunities for people to 
experience their cultural inheritance by offering special protection for 
cultural resources. 

The NPS Management Policies recognize five broad categories of cultural 
resources, with many resources often classified into multiple categories. 

Archeological resources are organized bodies of scientific evidence 
providing clues to the mystery of past events, primarily objects in 
context, ranging from household debris in a site from a past culture, to 
foundations of buildings, to pottery and tools, to paintings or writings. 

Cultural landscapes are settings humans have created in the natural 
world showing fundamental ties between people and the land, ranging 
from formal gardens to catde ranches, and from cemeteries or 
batdefields to village squares. 

Structures are large, mechanical constructions that fundamentally 
change the nature of human capabilities, ranging from Anasazi cliff 
dwellings to statues, and from locomotives to temple mounds. 

Museum objects are manifestations and records of behavior and ideas 
that span the breadth of human experience and depth of natural 



87 



REPORT TO CONGRESS: Effects on Cultural and Historic Resources, Sacred Sites, and Ceremonies 



history, and may include archeological resources removed from the 
context where they were found. 

Ethnographic resources are the foundation of traditional societies 
and the basis for cultural continuity, ranging from traditional arts and 
native languages, spiritual concepts and subsistence activities which are 
supported by special places in the natural world, structures with historic 
associations, and natural materials. 

An important aspect of cultural resources is their non-renewability: If they 
lose significant material aspect, context, associations, and integrity, they are 
lost forever. The responsibility of the NPS is to minimize loss of pre-historic 
and historic material. Closely related but secondary responsibilities include 
maximizing the expression of historic character, integrating site development 
with natural processes, sustaining the lifeways of ethnic groups, increasing 
our knowledge of past human behavior, and supporting the interpretation of 
park resources. 

Cultural resources of the NPS affected by overflights range from Anasazi cliff 
dwellings and museum objects, to the faces at Mount Rushmore, to Civil 
War batdefields and cemeteries, to religious ceremonies at Hawaiian 
temples, to the Statue of Liberty and the Jefferson National Expansion 
Memorial, to reenactment of important events in history or living examples 
of everyday life during an historical time period. They encompass museums, 
ships, and factories as well as paintings, clothing, dishes, books and fragile 
artifacts. 

Possible adverse aircraft overflight impacts on cultural resources entrusted to 
the NPS include physical impacts from vibrations, loss of historical or 
cultural context or setting, and interference with visitors' park experience. 
The term "adverse effect" has special meaning when used in association with 
historical properties. The definition put forth in The National Historic 
Preservation Act of 1 966 states: 

"An undertaking is considered to have an adverse effect when 
the effect on a historic property may diminish the integrity of the 
property's location, design, setting, materials, workmanship, 
feeling or association." 

While physical impacts can permanendy harm objects, impacts to context or 
setting, such as when aircraft fly over an 1 800's reenactment or an ancient 
religious ceremony, can significandy reduce the associations and integrity of 
the objects, and the enjoyment and understanding of the cultural heritage. 

Section 1 of Public Law 100-9 1 requires the NPS to assess the effects of 
aircraft overflights on historical and cultural resources: 



88 



4. ? Extent of Concern by Park Management and Visitors 



The research at each such [park] unit shall provide information 
and an evaluation regarding each of the following . . . 

"(3) other injurious effects of overflights on the natural, 
historical, and cultural resources for which such units were 
established. ..." 

At a large number of parks, cultural and historical resources are the focal 
point of the park. In many cases these resources were the primary reason for 
the park's creation, and they continue to be the reason for its existence. For 
example, cultural resource preservation is the primary mission at park units 
such as Chaco Culture National Historical Park, Canyon de Chelly National 
Monument, Colonial National Historical Park, Gettysburg National Military 
Park, Gila Cliff Dwellings National Monument, Mesa Verde National Park, 
Pu'uhonua o Honaunau National Historical Park, San Antonio Missions 
National Historical Park, Statue of Liberty National Monument, and 
numerous historical forts around the country. This section addresses 
whether overflights adversely affect cultural sites, structures, objects, as well 
as sacred sites and ceremonies. 



4.1 Extent of Concern by Park Management and 
Visitors 

Two recent surveys provide information on the extent and intensity of 
concern by park managers and by visitors. 

4. 1 . 1 Park Management Assessment 

Park managers are responsible for safeguarding the resources in their parks. 
Cultural and historical resources are no exception. In order to learn more 
about these concerns, in the context of aircraft overflights, the Park Manager 
Survey (HBRS, Inc., 1994) asked questions about cultural and historical 
resource preservation. Survey questionnaires were sent to 98 park managers 
whose units had been previously identified as having some level of aircraft 
overflight problems. The responses provided by the managers are reported 
below. Although the results cannot be applied to the entire National Park 
System, they reflect the perspective from nearly one-third of the units in the 
System with 76 percent of the acreage and 53 percent of the visitation. And 
they reflect the subset of park units where aircraft overflights have generated 
some level of concern. 

To determine the proportion of parks where cultural and historical resources 
were considered important, managers were asked how important it was for 
their park to provide an opportunity for visitors to appreciate the historical 
and cultural significance of the park. Their responses are shown in 



89 



REPORT TO CONGRESS: Effects on Cultural and Historic Resources, Sacred Sites, and Ceremonies 



Figure 4. 1 . Out of 91 park units responding, 90 percent of the managers said 
that providing this opportunity was "moderately," to "extremely" important 
to them. 

The managers were then asked the degree to which they felt aircraft activity 
interfered with their ability to provide this opportunity. Their ratings are 
shown in Figure 4.2. Opinions are clearly distributed across the entire range, 
from "not at all" to "extremely." However, over SO percent of the managers 
rated the degree of interference in their parks as "moderate" to "extreme," 
and over 1 percent rated interference in the "extreme" category alone. 



Importance of Park Historical/Cultural 

Opportunities (Managers Survey) 



70 



60 • ■ 



50-- 



40- 



30 ■■ 



20--- 



10-- 



Not at all 



Slightly Moderately 



16 



Very 




Extremely 



Figure 4. 7 : Management Rating of Importance of Providing 
Historical and Cultural Opportunities 



1 

en 


nterference with Historical/Cultural 

Significance (Managers Survey) 




Number of Managers 

— • K3 CO .b. L 
3 O O O O C 

1 1 1 l 1 








24 




18 










:;x;>:;:£:£:;:;x£:£:;x£: 




17 " 




1 


| 




10 


LI 




! 




Not at all Slightly Moderately Very Extremely 





Figure 4.2: Management Perspective on Interference with Opportunities 



90 



4. J Extent of Concern by Park Management and Visitors 



The responses provided by the managers to these two questions make two 
important points. First, cultural and historical resources exist in, and are 
important to, the vast majority of the 91 park units who responded to the 
survey. This finding suggests that the potential for impact exists in many park 
units. Second, the extent to which this potential has been realized is sizable. 
As was true in the case of managers' evaluations of overflights in general, (as 
discussed in Chapter 2), the. impacts in cultural and historic sites are judged 
to vary widely from park to park, with serious impacts occurring in some 
parks. 

4.1.2 Visitor Assessment 

During the spring, summer and fall of 1992, the NPS conducted the Visitors 
Survey of park visitors at 39 park units selected to represent the National 
Park System (McDonald et al. 1994). Of these, eight were primarily cultural 
or historical parks. The parks were selected through a very careful, 
system-wide sampling of NPS units in order to achieve a statistically valid 
sample of the entire National Park System (excluding Alaska). In this survey, 
visitors were asked to complete a brief questionnaire as they exited the park. 

As part of the survey, visitors were asked how much the sounds of aircraft 
interfered with their appreciation of the historical and/or cultural 
significance of the park. Figure 4.3 summarizes the responses from the eight 
cultural and historical parks sampled. A great majority of visitors felt that 
litde interference had occurred. Similarly, system wide only about two 
percent of the visitors (about 7 million visitors) reported a moderate to 
extreme degree of interference. 



CONCLUSION 4.1: 

Park managers believe that 
providing an opportunity for 
visitors to appreciate the 
historical and cultural 
significance of the parks is an 
important goal, and that 
aircraft overflights, in certain 
circumstances, can significantly 
interfere with that opportunity. 
A systematic approach for 
addressing overflights must 
account for any special cultural 
or historical opportunities 
provided by specific parks. 



20 



15 



Inteference with Historical/Cultural 

Significance (Visitors Survey) 

95.3 



=1 10 



5 ■■ 



8 "Cultural" Parks 



2.6 



07 0.6 

«'"' ! """" t ~>*.:. m .»*,.: 



0.8 



Not at all 



Slightly Moderately Very 



Extremely 



Figure 4.3: Visitor Ratings at Eight "Cultural" Parks of Aircraft Interferences 
with Historical and Cultural Significance of Park 



91 



REPORT TO CONGRESS: Effects on Cultural and Historic Resources, Sacred Sites, and Ceremonies 



CONCLUSION 4.2: 

There is no wide-spread impact 

on the appreciation of 

historical and cultural 

resources by visitors from 

aircraft overflights. But under 

certain combinations of aircraft 

overflights and cultural / 

historical park opportunities, 

visitors' experience may be 

impacted. The NPS believes 

this impact is occurring at a 

limited number of areas. 



These results present an expected difference from those of the managers' 
survey shown in Figure 4.2 (where 49 out of 9 1 managers reported 
moderate to extreme interference with their ability to provide cultural or 
historical opportunities). This difference is attributable to two primary 
factors: 

■ Managers have a greater awareness of the opportunities their parks 
have to offer than do most visitors; most visitors have little 
understanding of the cultural resources that are at risk. 

■ The Visitors Survey was designed to obtain a system-wide sample of 
visitor reactions at all parks, not visitor reactions at historical/cultural 
parks, whereas the manager survey was restricted to parks where 
aircraft overflight concerns had been previously expressed. 

As with other forms of impacts on visitors discussed in chapter 6, the impact 
on appreciation of the historical/cultural significance varies considerably park 
to park. Figure 4.4 shows for each of the Visitor Survey parks the percent of 
visitors reporting interference with appreciation of history/culture and the 
percent of visitors who reported hearing aircraft. Like the other impacts 
investigated, an understanding can be gained only by examining individual 
parks. 



Interference with History or Culture 

Visitors Survey Parks 



20 



15-- 



10-- 



5-- 



m 

: m 
m '■ 

--:*- 'J- : '" M " \ 

'■* ■ * - ; ; 



10 20 30 40 50 60 70 80 
Percent Respondents Who Heard AC 



90 100 



Figure 4.4: Percent of Visitors Reporting Interference with 
History or Culture at Specific Parks 



4.2 Acoustic Impact on Cultural and Historical Resources 

Because of the diversity in the cultural and historical resources of the 
National Park system, as well as in the types of aircraft overflights the parks 
experience, many types of impact can occur. For convenience, these impacts 



92 



4. 7 Extenf of Concern by Pork Monogemenf ond Visitors 



may be divided into two major categories (1) audible acoustic impact, and (2) 
noise-induced vibration. In addition, the NPS has some concern that the 
rotor wash from helicopters approaching too close to cliff dwellings could 
disturb materials in context (e.g., pollen, soils, etc.). Audible non-indigenous 
sound affects solemnity, natural quiet, and speech communication. 
Noise-induced vibration affects artifacts and structures. These impacts are 
addressed in subsequent subsections. 

The sound from aircraft activity can impinge on the solemnity of sacred sites 
as well as interfere with Native American ceremonies. National parks provide 
opportunities for quiet generally unavailable in common non-park settings. 
Such quiet park surroundings provide unique opportunities for visitors to 
experience cultural and historic sites in an historically accurate audible 
environment — the environment that existed before the introduction of 
mechanized power. 

An illustrative example of how overflights can impact site solemnity, speech 
communication, and historic structures is the situation at Taos Pueblo, one 
of the oldest living communities still existing in the United States, and a 
candidate World Heritage Site. In a 1992 letter and position paper on the 
subject of military overflights of the Taos Pueblo, pueblo spokesperson gave 
this overview of their problem: 

The Pueblo of Taos has serious concerns with continual 
overflights of aircraft which intrude into the sensitive areas of 
our village and our sacred wilderness lands under trust 
protection with the United States Government. 

Our Blue Lake Wilderness is a place of retreat and prayer to 
regain the Strength of Life for our People. Our sacred shrines lie 
throughout the region. Within our village is the place of 
ceremony where, within our Kivas and ancient homes, a season 
of quiescence is observed in reverence for the Earth. In 
recognition of these sacred ways and our ancient architecture, 
our village is denominated a National Historic Site and is under 
consideration as a World Heritage Site. Intrusions to our privacy 
cannot be tolerated, for they threaten the continuance of an 
ancient way of life. 

In recent years, we have experienced an astonishing increase of 
both proposed and actual airflight activity over Taos Pueblo 
lands. The FAA and Town of Taos have proposed a commercial 
air corridor directly over our village and wilderness, originating 
approximately three miles from our borders. This project is 
currently in the EIS process. Private overflights are increasing. 
During our annual Blue Lake pilgrimage, our People were 
buzzed by low-flying Cessna aircraft, sixty to eighty feet high. 



93 



REPORT TO CONGRESS: Effects on Cultural and Historic Resources, Sacred Sites, and Ceremonies 



attempting to film the sacred "Journey for Life." In 1991, the 
U.S. military proposed a low-level flight training corridor across 
our lands. This process has been temporarily halted from 
community outrage. Six months later, at least two out-of-state 
military bases adopted flight patterns across our wilderness, 
resulting in forty to seventy oven'lights a day. The flights 
alternate between low-level passes through our canyons, and 
B- 1 high-altitude refueling flights, which echo off the mountain 
passes because of the size of these bombers." 

In an earlier letter that year to the National Congress of American Indians on 
this subject, the Taos Pueblo more fully communicated the nature of their 
concern on this issue: 

"Under the traditional ways of Taos Pueblo, air is part of the 
'sacred realm' to which we hold inseparable responsibilities 
from land and water protection. Our ceremonial ways protect 
all things of the Earth and all things overlying the earth. It is 
impossible for us to conceive of adequately carrying forth our 
traditional responsibilities when we can no longer control what 
happens within the sacred realm of the "upper domain." 
Among our people, it is understood that there is no separation 
between Earth and the realm overlying the Earth. It is an 
inseparable extension of life and the responsibilities toward life. 

"These are concepts that are not understood by non-Indian 
people. Native American Indian people alone understand the 
unique responsibilities that Tribes hold toward the perpetuation 
of life, and how the successful outcome of our ceremonial 
responsibilities provide the link for human beings to maintain 
their connections to all life. 

The space overlying our sacred shrines and wilderness areas 
which are used for the perpetuation of tradition must be 
protected at all cost. Airspace to Native American Indian people 
is more than a resource for the generation of income. It is the 
sacred medium through which we make our connection the 
Spirit of Life, and through which all life is maintained." 

National parks in Alaska, Hawaii, and the contiguous 48 states contain 
abundant resources traditionally defined and used as sacred and subsistence 
grounds by Native Americans and others associated with areas now under 
NPS stewardship. Some resources that Native Americans define as 
meaningful fall into the historic preservation category of "cultural resources," 
or sites, structures, and landscapes. Others may be termed "natural 
resources" for land management purposes, but are defined culturally by 
Native Americans and other traditional user groups as places ot religious 



/ . October 5, / 992 Letter and position paper from the Taos Pueblo to Senator Daniel Inouye (Hawaii) seeking relief from military overflights of the pueblo. 
2. June 10, 1992 Letter from the Taos Pueblo to the National Congress of American Indians (NCAI) explaining the overflight issue at the Taos Pueblo. 



94 



4.3 Vibration Impact on Cultural and Historical Resources 



meanings. These include naturally configured shrines, power rocks and caves, 
ethnobotanical gathering areas, and traditional ceremonial hunting areas. 
Subsistence areas and wildlife, especially in Alaska, are among the resources 
invested with cultural significance for food-gathering purposes. 
Characteristically, Native American food-gathering also occurs within a 
religious context. 

Native Americans note that undisturbed habitats, particular resources, and 
contexts are pivotal to the success of religious practices. Contemplative 
activities involving communication with holy beings require the intense 
concentration that quiet, restful surroundings engender. Unnatural 
disturbances during religious ceremonies portend harm to traditional 
practitioners of sacred acts and their intended beneficiaries. Mark Schoepfle 
(Schoepfle, 1989), for example, suggests that ". . . disruptions may cause 
important supernatural power to be misdirected, at considerable peril to the 
beneficiary of the ceremony or medicine man or shaman. In these cases 
sickness or harm may require further ceremonial or religious intervention, at 
considerable expense to the people involved." In this same vein, Thomas 
Greider's work (Greider, 1993) for the U.S. Air Force on the effects of 
low-level flyovers on Native American religious practices indicates there is a 
noticeable effect on the practice of Native American curing ceremonies from 
the flyovers. 

Data on traditional ceremonials disrupted in parks by low-flying craft have 
not been systematically collected, but informal comments suggest problems. 
At risk, for example, from disruptive overflights are religious activities and 
practitioners associated with the Timbisha Shoshone Tribe who live at Death 
Valley National Park. Overflights at Grand Canyon can threaten religious 
activities of neighboring Hopi, Navajo, Hualapai, Havasupai, and Paiute. 
Observers have noted that on the flight corridors that run immediately south 
of the Kaibab Paiute Indian Reservation, adjoining Pipe Spring National 
Monument, caravans of B-52s can be observed traveling east to west close 
enough to the ground for their aircraft numbers to be read easily. 



4.3 Vibration Impact on Cultural and Historical 
Resources 



CONCLUSION 4.3: 

Just as the sound of overflights 
can impair opportunities for 
experiencing natural quiet, so 
too can these sound levels 
adversely affect not only the 
experience of visiting historic, 
cultural or sacred sites, but also 
the preservation of traditions 
that are an inherent part of a 
way of life. A process for 
identification and resolution of 
overflight impacts must 
recognize these significant 
adverse effects though they 
may be subtle to the 
uninformed. 



The sound from aircraft activity can cause archeological resources, 
structures, and museum objects to vibrate. Depending on the character of 
the sound, the effects range from audible rattle, to items "walking" across 
surfaces, to fatigue cracking, and potentially to direct or indirect structural 
damage (Hanson et aJ. 1991). Considerable government sponsored research 
has been conducted on the effects of aircraft noise on structures. Most of 



95 



REPORT TO CONGRESS: Effects on Cultural and Historic Resources, Sacred Sites, and Ceremonies 



this research, however, has been related to sonic booms. Research includes 
work sponsored by the U.S. Air Force (USAF) under its Noise and Sonic 
Boom Impact Technology (NSBIT) program, by the National Aeronautics 
and Space Administration (NASA), and by the FAA. Environmental impact 
assessments conducted by the USAF tor proposed low-level military training 
routes, measurements ot noise-induced vibration of buildings conducted by 
NASA near rocket launch sites, and measurements of airborne noise effects 
from blasting by the Bureau of Mines also provide valuable information. By 
comparison, only a limited number of vibration measurements have been 
conducted on archeological ruins exposed to fixed- and rotary-wing aircraft 
noise. This work has been conducted by the U.S. Geological Survey and the 
USAF Geophysics Laboratory. 

4.3. 1 How Structures Respond 

Airborne sound is a form of energy which travels in waves through the air. 
When sound waves encounter a structure or solid object, part of the energy 
is transferred to the structure and part is reflected. The portion which is 
transferred causes the object to vibrate. The magnitude of the resultant 
vibration is dependent on the characteristics of both the sound source and 
object itself. 

A very important characteristic of the structure is the way it responds to 
being shaken at different rates. Structures are very much like a series of 
springs and weights in die way in which they respond to acoustic pressure 
loadings. The type of construction (masonry, wood frame, etc.) determines 
both the springiness and the weight. Together, the springs and weights create 
natural frequencies in the structure. If structures are shaken at their natural 
frequencies they will vibrate more than if they are shaken at other 
frequencies, even though the shaking force is the same. 

An example of the natural frequency phenomenon may be observed by 
attaching a small weight to a rubber band (a weight sufficient to stretch the 
rubber band about 2 inches). Holding the rubber band between the fingers, 
if the rubber band is shaken very slowly (up and down about once per 
second) the weight moves up and down about the same distance as the hand 
inducing the motion. When the speed of the shaking (the frequency) is 
slowly increased, the weight will begin to travel a greater distance than the 
hand. As the frequency is increased further, this phenomenon will reach a 
maximum. Shaking at even greater frequencies will reduce the motion of the 
weight, and as the speed is increased even further, the weight will hardly 
seem to move at all. The rate of shaking which produced the maximum 
movement of the weight is the natural frequency of the system. 



96 



4.3 Vibration Impact on Cultural and Historical Resources 



The most important observation from the preceding experiment is that the 
weight moves a considerably greater distance than the source of the 
movement (the hand) when the system is shaken at its natural frequency. 
Tfie spring and weight system actually magnifies the amplitude of the motion. 
Buildings and structures behave the same way. Thus, seemingly minor 
acoustic pressure loadings on a structure can have significant damage 
potential. When the sound wave contains considerable energy in the vicinity 
of the structure's natural frequency, the damage potential is maximized. 
Typical natural frequencies of structures are in the region of 8 to 12 
complete cycles per second. The cause for concern is that sonic booms, 
helicopters and jets generate considerable energy at these frequencies. 

4.3.2 Types of Aircraft Noise That Can Excite Structural Response 

Damage potential from aircraft activity depends on the character of sound 
produced by the aircraft. For analytical purposes, aircraft sounds are divided 
into three categories: Sonic booms, subsonic fixed-wing noise, and 
helicopter noise. 

Sonic Booms. These are caused when an aircraft flying faster than the 
speed of sound passes an observer or structure. The result is a very brief 
pressure pulse similar to that shown in Figure 4.5 (Sutherland et al. 1990). 
Because of its shape it is frequendy called an "N-Wave." The amplitude of 
the wave can be very large, even when the aircraft is several miles away. 
During the wave, the pressure rapidly increases to a maximum (above 
atmospheric pressure), then decreases less rapidly to a minimum (below 
atmospheric pressure), and finally returns rapidly to atmospheric pressure. 
The upper peak of the "N" is the overpressure and the lower peak is the 
underpressure. These pressures are affected by the size, speed and altitude of 
the aircraft. 



Representative Sonic Boom "N-wave" Time History 



a 
o 
I 
< 

E 
o 



3 



Maximum Overpressure 



Atmospheric 
Pressure 




|from Sutherland, 1990J 



Time 



Figure 4.5. Representative Time History of a Sonic Boom "N-wave" Pressure Pulse 



97 



REPORT TO CONGRESS: Effects on Cultural and Historic Resources, Sacred Sites, and Ceremonies 



This wave usually sounds like two sharp booms in rapid succession (one from 
the steep initial part of the wave, and one from the steep return to 
atmospheric pressure). To a structure, however, the experience is much 
different. The structure generally responds to the lower frequency 
components of the pressure wave which are not audible to the human ear. 
The structure experiences a large push from the positive part of the wave, 
and then a pull from the negative part. Much like an ocean wave, the angle at 
which the wave encounters the structure determines whether particular 
surfaces experience the load of the wave head-on or as the wave ripples by. 
Either way, a unique bending load is placed on the structure. In general, the 
larger the surface, the greater the load because the pressure has a larger 
surface to act on. Sonic booms often produce sizable amounts of energy at 
the natural frequencies of structures. 

Subsonic, Fixed-Wing Flybys. Heavy aircraft (bombers) at close range 
can produce substantial low frequency energy. Depending on factors such as 
airspeed, wing area, and distance, heavy low-flying aircraft can generate 
substantial turbulent vortices. The vortices from heavy aircraft are of concern 
at all major airports because of their ability to compromise the safety of 
smaller aircraft following in their wake. The FAA has strict air traffic control 
guidelines to ensure adequate distance separation to prevent incidents. The 
same turbulent vortices of concern to the FAA can also place large turbulent 
loads on structures. . 

Subsonic, Rofary-Wing Flybys. Helicopters produce a substantial 
amount of their energy at the natural frequency of structures. The size of the 
rotor (which provides lift as well as propulsion) produces significant acoustic 
energy, and the relatively slow speed of the rotor causes this energy to be 
concentrated at low frequencies. In general, the heavier the helicopter, the 
greater the radiated low frequency energy. The main rotor is a very 
directional sound source: it produces sound that has unique radiation 
patterns depending on where the observer is located in relation to the 
aircraft. 

There are two important radiation phenomena of helicopters when it comes 
to structural response: blade vortex interaction, and "thickness" noise. Blade 
vortex interaction (sometimes referred to as "blade slap") occurs when the 
helicopter is in forward motion. A blade passing along the back side of the 
aircraft encounters (slaps) the turbulent wake created a fraction of a second 
earlier by another blade passing along the forward side of the aircraft. This 
sound radiates down and to the front of the aircraft, as shown in Figure 4.6. 
It is very directional, and not audible after an aircraft passes overhead. 

Thickness noise from helicopters is not routinely experienced by observers 
on the ground. This is because the noise generating phenomenon radiates 
sound only in a narrow angle (± 10 degrees) above and below the plane ot 



98 



4.3 Vibration Impact on Cultural and Historical Resources 



the main rotor, as shown in Figure 4.7. Hence, an observer must be at about 
the same elevation as the aircraft to observe thickness noise. Substantially 
more energy at the natural frequency of structures is radiated in thickness 
noise than in blade vortex interaction. 





CONCLUSION 4.4: 

Aircraft overflights create 
sound levels of frequencies low 
enough to induce natural 
frequency vibrations in 
structures. Supersonic aircraft 
flight, overflights by very large 
aircraft, and helicopters can all 
produce levels that may cause 
structural vibrations. In the case 
of subsonic flight, the aircraft 
must fly relatively near the 
structure for vibrations to be 
great enough to result in risk of 
damage. 



Figure 4.6: Helicopter "Blade Slap" Sound Wave Impinging on a Historical Site 




Thickness noise 



Figure 4.7: Helicopter "Thickness" Noise Radiating to a Cultural Resource 



4.3.3 Damage Potential 

Damage potential from aircraft activity also depends on the structure itself. 
Structural vibrations, especially with repeated exposures, can eventually lead 
to structural damage of irreplaceable resources. These resources include 
historical and archeological structures such as sites on the National Register 
of Historic Places and National Landmarks, and under certain circumstances, 
archeological sites and artifacts and cultural resource objects inside 
structures. In looking at damage potential, there are short-term and 
long-term effects. 



99 



REPORT TO CONGRESS: Effects on Cultural and Historic Resources, Sacred Sites, and Ceremonies 



Short-Term Effects. A short-term effect is one in which one or two noise 
events are sufficient to produce a permanent displacement in a structural 
element. A collapsed root, or a broken window are dramatic examples of 
acoustic pressure loads that are capable of producing structural failure or a 
major compromise to structural integrity in only a few flexure cycles. 
Bric-a-brac or historical artifacts falling off shelves is another example. These 
effects are most often associated with large amplitude single events such as 
sonic booms. Damage risk criteria have been developed for different types of 
construction, and boom strength estimating procedures have been developed 
for different types of aircraft and supersonic maneuvers. Together, they 
provide a first level means for predicting damage potential. 

Long-Term Effects. More insidious are the long-term effects created by 
repeated exposures at lower acoustic levels. While the dramatic effects of 
sonic booms can result from only a few, large-amplitude pressure cycles, 
equal damage can be accomplished with greater numbers of lower amplitude 
pressure cycles (a single helicopter hovering for 30 seconds with a blade 
passage rate of 12 per second would produce 360 pressure cycles). In 
contrast to a major structural displacement, the smaller pressure cycles may 
initiate a slower process consisting of three stages: 1 ) fatigue cracking, 2) 
moisture damage, and 3) erosion damage. The lower amplitude acoustic 
pressure cycles can initiate fatigue cracking. Although these cracks are often 
no more than hairline in width, they begin when britde materials, such as 
masonry, are momentarily stretched beyond their breaking strength. Careful 
observations have confirmed that repeated exposures to acoustic excitations 
produce ever-widening cracks. Most masonry construction is particularly 
vulnerable because of its britde nature. Mortar joints, as well as plaster or 
mud veneers, are construction elements most susceptible to fatigue cracking. 

Once fatigue cracking has begun, nature can complete the damage without 
further assistance (although repeated exposure to acoustic loads hastens the 
process). Mortar joints are important to masonry structures because they 
hold the various building blocks of the structure together. Veneers are also 
important because they act as moisture seals to protect the more vulnerable 
interior core wall constructions, particularly adobe, brick or rubble. Once a 
crack has been initiated (or accelerated) by acoustic excitation, moisture 
penetration can occur. The moisture then initiates a further disintegration 
process, either by eroding the structural integrity of a wall or roof direcdy, or 
by feeding the forces of freeze-thaw cycles. Freeze-thaw cycles are 
particularly damaging after moisture invasion has occurred because the 
freezing moisture expands and widens cracks even further. As cracks widen, 
further moisture is admitted and the process accelerates. Eventually, erosion 
occurs, and in time the structure is finally compromised. 



TOO 



4.3 Vibration Impact on Cultural and Historical Resources 



This entire process may take several years to occur, but the origins are in the 
initial fatigue cracking. The length of time between the initial cracking and 
the final collapse of a structure can be years or decades depending on the 
natural forces at work. This slow process, along with myriad intervening 
factors, makes it difficult to prove conclusively that any particular structure 
failed due to aircraft noise exposure alone, or even that the process was 
hastened by such exposure. 

Damage risk criteria have been developed for heavy fixed-wing aircraft and 
also for helicopter flyovers. The major risk factors identified are low-flying 
heavy helicopters and bomber aircraft. Lacking however, are risk assessments 
for potentially equally damaging exposures of aircraft flying at the same 
elevation as structures (such as cliff dwellings), an emerging area of interest 
to the air tour industry. Neither the effects nor the acoustic loads have been 
carefully documented for this activity. 

4.3.4 Mitigation 

Mitigation is a three step process. It involves: 1) assessing the acoustic 
pressure levels associated with potentially damaging aircraft activity, 2) 
identifying the types and structural conditions of vulnerable structures, and 
3) predicting the damage risk for the identified combinations of acoustic 
loads and structures. Currendy, no formal compendium is available enabling 
park managers to assess for themselves the potential impacts of different 
types of aircraft activity to be encountered in parks. Sound level prediction 
methods have been developed for subsonic aircraft (fixed- and rotary- wing), 
and for supersonic activity. Risk assessments have been published by various 
researchers for particular combinations of aircraft operations and structures. 
While much is known, some areas of risk assessment are incomplete. Most 
noteworthy for the absence of criteria is the damage risk posed by 
helicopters flying at the same elevation (or vertically within ± 10 degrees) of 
at-risk structures. 

Much of the damage risk assessment literature focuses on probabilities of 
damage from single occurrences of acoustic events. Estimates of cumulative 
effect, the probabilities of damage from continued and repeated exposures, 
are also available. The best available cumulative effect information is crucial 
to NPS planning because long-term assessment strategies are needed to 
preserve valuable resources over very long periods of time. Perhaps the best 
mitigation method to prevent potential adverse effects to nationally 
recognized cultural resources is by establishing standoff distances. 



CONCLUSION 4.5: 

Cause and effect are extremely 
difficult to determine for 
sound/vibration induced 
damage to structures. 
Accordingly, the NPS needs to 
develop a systematic method to 
inventory sensitive structures 
likely to be subject to 
potentially damaging sound 
exposures, and prepare 
methods for minimizing 
damage risk. 



CONCLUSION 4.6: 

Some damage risk criteria are 
available, but important areas 
of information regarding 
long-term exposure and 
helicopter sound levels are not. 
If the NPS is to develop 
guidelines for minimizing risk to 
structures, such guidelines will 
require additional data, or they 
should be based on 
conservative (protective) 
assumptions about 
vibration-induced damage. 



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REPORT TO CONGRESS: Effects on Cultural and Historic Resources, Sacred Sites, and Ceremonies 



4.4 Summary 

NPS managers believe overflights interfere with the historical or cultural 
significance of some national parks. Across the National Park System an 
estimated 4-5 million visitors feel their opportunities to experience the 
historical and cultural resources in parks is impacted. However, this small 
percentage of park visitors increases significandy at parks where managers 
perceive overflight problems. Consequendy, the NPS finds that aircraft 
overflights are impacting a limited number of cultural and historical parks in 
the National Park System. Studies show that at parks where aircraft overflight 
problems are perceived, visitors do indeed notice aircraft and react to them. 
And it is clear that although there is a need for a systematic approach to 
problem solving, it must be flexible enough to respond to unique 
park-by-park, location-by-location problems. 

Resolving NPS concerns will require addressing how to prevent vibration 
related damage from occurring, how to prevent loss of historical or cultural 
context, how to ensure solemnity for sites and ceremonies, and how to 
provide interpretation for visitors without serious speech interference. 



102 



5 



EFFECTS OF OVERFLIGHTS ON WILDLIFE 



5.1 Introduction 

In general, wild animals do respond to low-altitude aircraft overflights. The 
manner in which they do so depends on life-history characteristics of the 
species, characteristics of the aircraft and flight activities, and a variety of 
other factors such as habitat type and previous exposure to aircraft. The 
potential for overflights to disturb wildlife and the resulting consequences 
have drawn considerable attention from state and Federal wildlife managers, 
conservation organizations, and the scientific community. This issue is of 
special concern to wildlife managers responsible for protecting populations, 
and to private citizens who feel it is unwise and/or inappropriate to disturb 
wildlife. Two types of overflight activities have drawn the most attention with 
regard to their impacts on wildlife: 1) low-altitude overflights by military 
aircraft in the airspace over national and state wildlife refuges and other wild 
lands, and 2) light, fixed-wing aircraft and helicopter activities related to 
tourism and resource extraction in remote areas. 

The primary concern expressed is that low-level flights over wild animals 
may cause physiological and/or behavioral responses that reduce the animals' 
fitness or ability to survive. It is believed that low-altitude overflights can 
cause excessive arousal and alertness, or stress (see Fletcher 1980, 1990, 
Manci et al. 1988 for review). If chronic, stress can compromise the general 
health of animals. Also, the way in which animals behave in response to 
overflights could interfere with raising young, habitat use, and physiological 
energy budgets. Physiological and behavioral responses have been repeatedly 
documented, that suggest some of these consequences occur. While the 



103 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



SOCFRPart 17.3 



behavioral responses by animals to overflights have been well-documented 
for several species, few studies have addressed the indirect consequences. 
Such consequences may or may not occur, and may be detectable only 
through long-term studies. 

The scientific community's current understanding of the effects of aircraft 
overflights on wildlife are found in the literature. Such studies identify: 
collision with aircraft (Burger 1985, Dolbeer er al. 1993); flushing of birds 
from nests or feeding areas (Owens 1977, Kushlan 1979, Burger 1981, 
Anderson and Rongstad 1989, Belanger and Berad 1989, Cook and 
Anderson 1990); alteration in movement and activity patterns of mountain 
sheep (Bleich et al. 1990); decreased foraging efficiency of desert big horn 
sheep (Stockwell and Bateman 1991); panic running by barren ground 
caribou (Calef et al. 1976); decreased calf survival of woodland caribou 
(Harrington and Veitch 1992); increased heartrate in elk, antelope, and 
rocky mountain big horn sheep (Bunch and Workman 1993); and adrenal 
hypertrophy in feral house mice (Chesser et al. 1975). Over 200 published 
and unpublished reports can be found on the subject. These reports range in 
scientific validity from well designed, rigorous studies to professional natural 
resource manager and pilot reports. 

Recent concerns have focused on the significance of impacts as they affect 
wildlife populations. Defining a population as "a group of fish or wildlife in 
the same taxon below the subspecific level, in common spatial arrangements 
that interbreed when mature," it is possible to draw the conclusion that 
impacts to wildlife populations are occurring from low level aircraft 
overflights. This assertion is supported by numerous studies including the 
following: 

■ decreased calf survival of woodland caribou (Harrington and Veitch 
1992) 

■ disturbance to wintering snow geese documents the effects on 
staging/wintering subgroup (Belanger and Beard 1989) 

■ impacts on nesting herring gulls documents effects on a subgroup 
during production periods (Burger 1991) 

Additional research will be required to fully address the significance of such 
population impacts. However, waiting for and relying on future research 
results for current policy decisions is not possible. Therefore, it is necessary 
to make informed decisions recognizing that all of the consequences of 
disturbance will not be completely understood. 



104 



5.2 Physiological Responses to Aircraft Overflights 



5.2 Physiological Responses to Aircraft Overflights 

When disturbed by overflights, animal responses range from mild 
"annoyance," demonstrated by slight changes in body position, to more 
severe reactions, such as panic and escape behavior. The more severe 
reactions are more likely to have damaging consequences. Studies of aircraft 
impacts suggest that whether or not disturbance occurs, and whether or not 
disturbance has a harmful effect depends on a variety of characteristics 
associated with both the animal and with the aircraft. 

When the sudden sight and/or sound of aircraft causes alarm, the 
physiological and behavioral responses of animals are characterized as 
manifestations of stress. The effects of chronic stress from overflights have 
not been formally studied, though several national wildlife refuge managers 
suspect that stress from overflights makes waterfowl more susceptible to 
disease (Gladwin et al. 1987, US Fish and Wildlife Service 1993). Other 
types of disturbance-induced stress have been documented to produce a 
variety of other problems, such as toxemia in pregnant sheep (Reid and 
Miles 1962) and abnormal births (Ward 1972, Denneberg and Rosenberg 
1967). That exposure to low-altitude aircraft overflights does induce stress in 
animals has been demonstrated. Heart rate acceleration is an indicator of 
excitement or stress in animals, and increased heart rates have been shown 
to occur in several species exposed to low-altitude overflights in a wild- or 
semi-wild setting. Species that have been tested include pronghorn, elk, and 
bighorn sheep (MacArthur et al. 1982, Workman et al. 1992o,fc,c). Stress 
responses such as increased heart rates by themselves are an adaptation for 
encounters with predators and other environmental threats, which 
presumably must be faced daily. It is not known, therefore, if the addition of 
stressful events such as overflights actually harm animals. It may be that a few 
overflights do not cause harm, but that overflights occurring at high 
frequencies over long periods of time, do. 

Biologists caution that the consequences of disturbance, while cumulative, 
are not additive. Effects could be synergistic, especially when coupled with 
natural catastrophes such as harsh winters or water shortages (Bergerud 
1978, Geist 1994). Also, the tendency for additional stress to be harmful 
probably depends on other factors, such as the general health of animals to 
begin with. Some species are likely to be more susceptible to damage than 
are others. Research has shown that stress induced by other types of 
disturbance produces long-term, deleterious effects on the metabolism and 
hormone balances in wild ungulates (hoofed mammals) such as bighorn 
sheep (Geist 1971, Stemp 1983). Many animal biologists maintain that 
excessive stimulation of the nervous system can amount to chronic stress, 
and that continuous exposure to aircraft overflights can be harmful for the 
health, growth and reproductive fitness of animals (see Fletcher 1980, 1990 
for review). 



105 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



CONCLUSION 5.1: 

Overflights can induce 

physiological responses in 

animals, such as increased 

heart rates, but whether or not 

such responses cause harm is 

unknown. Effects may be 

synergistic, as when combined 

with natural events such as 

harsh winters or water 

shortages. 



The auditory systems of some animals may be particularly susceptible to 
physical damage, and such animals may experience hearing loss from 
exposure to chronic aircraft sound. Animals living in quiet desert 
environments have evolved particularly fragile ears and hence appear to be at 
great risk of sound-induced hearing damage (Bondello and Brattstrom 1979, 
Fletcher 1990). While aircraft noise and its effects on animal hearing have 
not been tested, other types of sound such as motorcycle noise have been 
shown to cause hearing loss in desert species, including the desert iguana 
(Bondello 1976) and the kangaroo rat, an endangered species (Bondello and 
Brattstrom 1979). Hearing loss can occur after as litde as an hour of 
exposure to loud noise, and can be temporary or permanent, depending on 
the degree of exposure to sound and the susceptibility of the individual 
animal. 



5.3 Behavioral Responses to Aircraft Overflights 

Behavioral responses of wild animals to overflights nearly always accompany 
physiological responses. Behavioral responses reflect a variety of states, from 
indifference to extreme panic. To some extent, responses are 
species-specific, whereby some species are more likely to respond in a 
certain manner than are others. However, even within a species, individual 
animals vary. Documented variations between individuals may be due to 
differences in temperament, sex, age, prior experience with aircraft, or other 
factors. For these reasons, anecdotal information about one animal's 
response to an overflight is not useful for drawing conclusions for that or any 
other species. Often, animals exhibit very subde and seemingly minor 
behavioral responses to overflights. Minor responses that are typical of both 
birds and mammals include head-raising, body-shifting, and turning and 
orienting towards the aircraft. Animals that are moderately disturbed usually 
show "nervous" behaviors such as trotting short distances (mammals), 
standing up with necks fully extended and scanning the area, or walking 
around and flapping wings (birds). 

When animals are more severely disturbed, escape is the most common 
response. Perching or nesting birds may flush (fly up from a perch or nest) 
and circle the area before landing again. Some birds, particularly waterfowl 
and seabirds, may leave the area if sufficiendy disturbed. There are dozens ot 
reports, mosfly from national wildlife refuges, of waterbirds flying, diving or 
swimming away from aircraft (e.g. U.S. Fish and Wildlife Service 1993). 
This is apparendy a widespread and common response. Bird flight responses 
are usually abrupt, and whole colonies of birds often flush together. 
Disturbed mammals will run away from overflight paths. Table 1 lists 
behavioral responses to overflights that have been documented during studies 
and incidental observations. 



106 



5.4 Indirect Effects of Disturbance from Overflights, and Consequences for Animals 



This table was generated from a review of published literature on the subject. 
Reports varied widely in how information was gathered. Aircraft altitudes are 
noted where known. Some reports are from rigorous studies, others from 
anecdotal information. In general, more severe responses (such as panic and 
escape) were a result of lower-altitude overflights. Responses that were not 
described in detail are in quotation marks. 

As Table 1 illustrates, only a handful of the thousands of animal species in 
the United States have been studied for their responses to overflights. Also, a 
disproportionate number of studies have concentrated on ungulates such as 
caribou and bighorn sheep. Carnivorous mammals have been virtually 
ignored, as have marine mammals, small mammals, and bats. Birds are more 
evenly represented, with studies on waterfowl, shorebirds, marine birds, and 
raptors, although songbirds and owls are notably absent. Reptiles and 
amphibians have never been studied for responses to aircraft. This uneven 
distribution of species representation is likely a result of two factors: 1) 
researchers acknowledge that some species are more susceptible to harm 
than are others, and have allocated efforts accordingly; and 2) some animals 
are easier to study than others. 

Generally, fish have not been considered at risk from aircraft disturbance. 
Because most fish and other aquatic organisms live entirely below the surface 
of the water, they do not experience the same sound levels that terrestrial 
animals do. Marine mammals (besides dolphins and whales) are an exception 
because they spend time above water, on shore. Data on behavioral 
responses of marine mammals to aircraft overflights are scarce. However, a 
study at Copalis National Wildlife Refuge in Washington State (where the 
U.S. Navy conducted pilot training from 1944 to 1993) reported responses 
of harbor seals and northern sea lions to military A-6 jet overflights as 
ranging from no response to abrupdy leaving resting sites on the rock shore 
and entering the sea (Speich et al. 1987). California gray whales and harbor 
porpoises, conversely, showed no obvious behavioral responses during this 
study. 



CONCLUSION 5.2: 

Researchers have documented 
a range of wildlife behavioral 
responses to aircraft 
overflights. Variations in 
response may be due to 
differences between individuals, 
and anecdotal information 
about one animal's response is 
not useful for drawing 
conclusions regarding that or 
other species. Behavioral 
responses may be subtle. 



5.4 Indirect Effects of Disturbance from Overflights, 
and Consequences for Animals 

The behavioral responses to aircraft overflights described above are direct, or 
immediate, responses. Biologists and others are concerned that indirect 
effects of these responses may have harmful consequences for animals, 
especially when overflights (and responses) are frequent. Behavioral reactions 
have the potential to cause injury, to influence breeding success, energetics 
and habitat use, and to result in bird strikes. Whether or not such indirect 
effects occur depends on other factors associated with the natural history of a 



107 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



species. Some animals are more susceptible than others to disturbance, 
because of unique life history patterns such as colonial breeding, habitat 
requirements, and restricted distribution. Others may need special 
protection during certain periods. Indirect effects are difficult to detect. 
However, some effects, such as habitat avoidance, have been detected (e.g. 
McCourt et al. 1974, Schweinsburg 1974k, Krausman et al. 1986). 
Large-scale consequences such as permanent habitat abandonment or 
regional or national population declines have not been well documented, 
though some experts suspect that they occur. For example, refuge managers 
at Key West National Wildlife Refuge suspect that the only known colony of 
magnificent frigatebirds in the United States is declining due to frequent 
low-altitude overflights by tour planes (Gladwin et al. 1987). 



TABLE 1 : GENERAL RESPONSES BY SPECIFIC ANIMAL SPECIES TO AIRCRAFT OVERFLIGHTS 


Species 


Response 


Aircraft 2 


Flight 
Altitude 3 


Reference 


Large Mammals 


Pronghorn 


Accelerated heart rate 
Run short distance 
Bolt and run 


FW 
MJ 
H 


500 

5000 

100 


Workman et. al. 1992a 


No response 

Stop feeding, tense muscles 

Run 


H 


150-400 


Luz & Smith 1 976 


Mule Deer 


No response 

Minor behavior changes 


MJ 


<3000 


Lamp 1 989 


Bighorn Sheep 


Accelerated heart rate 


MJ 
FW 
H 


5000 
100 
100 


Workman et al. 1992b 


Decrease food intake while 

feeding (interruption) 
Take more steps while feeding 


H 


— 


Stockwell et al. 1991 


No response 
Accelerated heart rate 
Run 


H 
H 


1 640-4920 
490-660 


Mac Arthur et al. 1979 


No response 

Minor behavior changes 

Leave area 


MJ 


<3000 


Lamp 1989 


Leave area 


H 


160-650 


Bleich et al. 1 990 


No response 

Interrupt normal activities 
Run <330 feet 
Run .62-1.2 es 


FW 


100-990 


Krausman & Hervert 1983 



2. FW — small, jixed-wing aircraft, H — helicopters, MJ — military jet aircraft, C = commercial jet aircraft. 

3. Aircraft flight altitudes in feet, rounded to nearest 10. 



108 



5.4 Indirect Effects of Disturbance from Overflights, and Consequences for Animals 



TABLE 1 : continued 


Species 


Response 


Aircraft 2 


Flight 
Altitude 3 


Reference 


Large Mammals continued 


Bighorn Sheep continued 


Run > 1 mile 


H 


— 


Horejsi 1975 
Kigerl970 


Desert Mule Deer 


No movement 

Move <. .6 mile to new habitat 


FW 


260 


Krausman et al. 1986 


Elk 


Accelerated heart rate 


Ml 
H 


5000 
100-500 


Workman et. al. 1992c 


Congregate together 
Watch aircraft 


Ml 


— 


McCullough 1969 


Run away 


H 


— 


Jorejsi 1 975 


Mountain Goat 


React "adversely" 
May abandon area 


H 


— 


Ballard 1975 


Run away 


H 


— 


Horejsi 1975 


Are "terrified" 
May abandon areas 


H 


— 


Chadwickl973 


Dall Sheep 


No response 
Get "excited" 
Do not abandon habitat 


FW 


— 


Nichols 1972 


Run away 


H 
FW 


— 


Feist etal. 1974 
Schweinsburg 1974a 


Alarm behavior 
Crowd together 


FW 
H 


— 


Linderman 1972 


React "severely" 


H 


— 


Andersen 1971 


Gray Wolf 


Initially freight response, 
(scatter, run), later accept 


FW 


260 


Krausman et al. 1986 


Grizzly Bear 


Run 
Hide 


FW 
H 


— 


Harding & Nagy 1976 


"Mild" behavior response , 
Run away 


H 


>3280 


Ruttan 1974 


Run in "panic" 
Hide (may associate aircraft 
with capture) 


H 


— 


Pearson 1 975 


Interrupt activity, leave area 
Run towards cover 


FW 


>1000 
200-500 
200-500 


McCourtetal. 1974a 
Klein 1973 


Bison 


No response 


MJ 


— 


Frazier 1 972 


No response 
Run 1 minute 
Run 5 miles 


FW 


200-490 


Fancy 1982 


Reindeer 


Crowd together, panic 


FW 
H 


<100 
<100 


Ericson 1972 


Run away 


FW 


— 


Slaney & Co. Ltd. 1 974 



109 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



TABLE 1 : continued 


Species 


Response 


Aircraft 2 


Flight 
Altitude 3 


Reference 


Large Mammals continued 


Caribou 


Move short distance 
Rarely leave area 


FW 


— 


Staney & Co. Ltd. 1 974 


No response 
Panic, flee 


FW 
H 


200-500 
200-500 


Klein 1973 


Walk, trot, gallop away 
Momentarily stop feeding 


H 


980 


Gunnetal. 1985 


Panic, escape 


FW 

H 


500 
500 


Calefetal. 1976 


Brief startle response 

Run for 8-27 seconds 

No effect on daily activity 

No effect on distances traveled 


Ml 
H 


100-500 
100-500 


Harrington & Veitch 1991 


Mothers and calves not 
separated 


H 


— - 


Miller & Broughton 1 973 


Run away from area 


FW 


— 


Valkenburg & Davis 1985 


Minor changes in behavior 
Panic and run 


FW 
H 


<1300 
<1300 


Miller & Gunn 1979 


Calves died from trampling 
during escape from either 
wolves or aircraft 




— 


Miller & Broughton 1974 


Calves died 


MJ 


— 


Harrington & Veitch 1992 


Panic and escape 


H 

FW 


<790 
<790 


Surrendi & DeBock 1976 


Small Mammals 


House mouse 


Enlarged adrenal glands 


C 




Chesseretal. 1975 


Marine Mammals 


Atlantic Walrus 


Raise head towards aircraft 
Shift body position 
Leave rocks, enter ocean 


H 


4270 


Salter 1979 


Harbor Seal 
Northern Sea Lion 


Leave rocks, enter ocean 


MJ 


<500 


Speichetal. 1987 


Raptors 


Bald Eagle* 
Golden Eagle 
Peregrine Falcon 
Gyrfalcon 
Rough-legged Hawk 


No response 

Panic, frantic escape 

No effect on raising young 


H 




White & Sherrod 1973 


Peregrine Falcon* 
Cooper's Hawk 
Common Black Hawk 
Harris' Hawk 
Zone-tailed Hawk 
Red-tailed Hawk 
Golden Eagle 
Prairie Falcon 


"Minimal response" 
Alarm behavior 
Fly from perch or nest 
No effect on raising young 


MJ 


<980 


Ellis etal. 1991 



110 



5.4 Indirect Effects of Disturbance from Overflights, and Consequences for Animals 



TABLE 1: continued 


Species 


Response 


Aircraft 2 


Flight 

Altitude 3 


Reference 


Raptors continued 


Osprey 


No effect on raising young 


H 


— 


Carrier & Melquist 1976 


Rarely leave nest 

No effect on raising young 


FW 
H 


— 


Poole 1989 


Northern Harrier 


No response 


Ml 




Jackson etal. 1977 


Peregrine Falcon 


No response 
"Severe" response 


H 


<2000 


Ritchie 1987 


Gyrfalcon 


Fly away 

Alert behavior 

No nest abandonment 

No effect on daily activity 

patterns 
May avoid returning to breed 

in following years 


H 
FW 


500-1000 
500-1000 


Piatt 1975 
Piatt & Tull 1977 


Prairie Falcon 


Flush from perches 


H 


— 


Craig & Craig 1 984 


Red-tailed Hawk 


No response 
Flush from perches 


H 


— 


Craig & Craig 1 984 


Golden Eagle 


No response 


H 


— 


Craig & Craig 1984 


Ferruginous Hawk 


No response 


FW 


<100 


White & Thurow 1 985 


Red-tailed Hawk 


Flush from nests 

No effect on raising young 


H 


100-150 


Andersen et al. 1989 


Waterbirds 


Brant* 

Emperor Geese 
Canada Geese 


No response 
Alert behavior 
Flight 


FW 

H 


0-500 
0-500 


Ward&Stehn 1989 


Oldsquow* 
Surf Scoter 


Swim away 
Dive into water 
No response 


H 


100-750 


Ward & Sharp 1974 


Oldsquow* 
Surf Scoter 


Escape 

Alert Behavior 
Dive into water 
Flock together 
Change activity budgets 
(resting, feeding, sleeping) 


H 


100-750 


Gollopetal. 1974a 


Migrating ducks* 
(various species) 


No reaction 

Minor behavior changes 

Flush from lakes 


Ml 


<3000 


Lamp 1989 


Ducks and geese* 
(various species) 


Fly away 
Swim away 
Dive into water 
Abandon some lakes for 
>4 days 


FW 




Schweinsburg 1974a 
Schweinsburg 1974b 


Canada goose 


Arouse from sleep 
Alert behavior 
Call 


Ml 


<3000 


Lamp 1 989 



111 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 

















Species 


Response 


Aircraft 2 


Flight 
Altitude 3 


Reference 


Waterbirds continued 


Trumpeter Swan 


Stop activity; head up 
Flush from nests 


FW 
H 
C 


200-2000 


Henson& Grant 1991 


Seek cover in tall vegetation 
Cygnets crowd together 


FW 
H 


740-990 
500 


Shandruk & McCormick 1989 


Snail Kite 


No response 
Watch aircraft 


C 


— 


Synderetal. 1978 


Brant 


Panic and escape area 


FW 
H 


<500-1000 


Henry 1980 


Fly away 

Widespread "panic" 
Lost feeding time 


FW 

H 


<1650 


Owens 1 977 


Brant* 

Glaucous Gull 
Arctic Tern 


Flush from nests 
Disrupt nesting behavior 


FW 
H 


500-1000 
500-1000* 


Gollopetal. 1974b 


Common Eider 


No effect on nesting behavior 


FW 
H 


— 


Gollopetal. 1974b 


Tufted Puffin* 

Brant 

Double-crested Cormorant 

Common Murre 

Glaucous Gull 


No response 
Wing-flapping 
Flush from perches 
Abrupt departure of area 


MJ 
Ml 


>500 
>500 


Speichetal. 1987 


Sooty Tern 


May disrupt breeding 
May cause hatching failure 


MJ 


Supersonic 


Austin etal. 1970 


Crested Tern 


Scan sky 
Alert behavior 
Startle and escape 


C 


250-1000 


Brown 1 990 


White Pelican 


Stampede, panic 

Eggs lost, abandoned, eaten 


C 


>33 


Bunnell etal. 1981 


Herring Gull 


No effect on breeding 
No response 


c 


— 


Burger 1981 


Flush from nests 

Eggs broken, lost, eaten 


c 


Supersonic 




Cattle Egret* 
Double-crested 
Cormorant 
Great Blue Heron 
Great Egret 
White Ibis 


No effect on colony 

establishment 
No effect on colony size 
No effect on nesting behavior 
No effect on breeding success 


MJ 


<500 


Black etal. 1984 


Oldsquaw* 
Scaup species 
Redhead 
Canvasback 


Flush up and away from lake 


H 




Christiansen & Younge 1979 


Snow Goose 


Raise head 

Crowd together, call 

Stop feeding, 

Fly away (return in 5 min.) 


FW 

H 




Davis & Wisely 1 974 



112 



5.4 Indirect Effects of Disturbance from Overflights, and Consequences for Animals 



TABLE 1: continued 


Species 


Response 


Aircraft 2 


Flight 
Altitude 3 


Reference 


Waterbirds continued 


Snow Goose continued 


No response 
Minor behavior changes 
Flush, circle over, depart or 
land again 


MJ 


<3000 


Lamp 19891 


Leave lake area 


FW 


98-9800 


Spindler 1983 


Flush from lakes 


FW 


300-1000 


Salter & Davis 1 974 


Kittiwake* 
Northern Fulmar 


Stay on nest (no response) 


H 


— 


Dunnett 1977 


Brunnich's Quillemot* 
Kittiwake 


No response 

Flush from nests 

No egg or chick losses 


H 


0.5-3 miles 
distant 


Fjeld etal. 1988 


Snow Goose* 

Canada Goose 
Purple Gallinule 
Northern Pintail 
American Coot 


Flush 


H 




Edwards et al. 1979 


Pacific Eider 


No response 


H 


— 


Johnson etal. 1987 


Great Egret* 
Snowy Egret 
Louisiana Heron 


Flush from nest, return <5 

minutes 
No response 


FW 
H 


395 


Kushlan 1979 


Songbirds 


Lapland Longspur 


No avoidance of nest sites 
Nestlings died 


FW 
H 


50 


Gollopetal. 1972 


Game birds 


Chukar 


Flush 

No response 


MJ 


<3000 


Lamp 1 989 


'Studies of more than one species generally documented all of the listed responses occurring by all of those species. 



5.4.1 Accidental Injury 

A common concern among biologists is that animals will occasionally fall, run 
into objects, or become trampled when they panic and run from aircraft. 
For example, at Cabeza Prieta National Wildlife Refuge, it was reported that 
a low-flying helicopter startled a deer, which ran off of a 26-foot cliff and 
broke its leg (USFWS 1993). Young ungulates are especially vulnerable to 
being trampled. One study of caribou calf mortality documented that three 
young caribou were trampled during panic and flight from either wolves or 
aircraft (Miller and Broughton 1974). Startle responses that cause panic and 
quick movements are most likely to cause injuries to animals in rugged 
topography (boulder fields, cliffs, scree slopes), at river crossings, or on icy 
ridges, especially when animals are grouped closely together (Harrington 
andVeitch 1991). 



113 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



5.4.2 Reproductive Losses 

For many species, it has been argued that disturbance could cause 
reproductive losses by altering patterns of attendance to young. Disturbed 
mammals and birds have been noted to run or fly away from the stimulus 
(i.e. the aircraft), and leave eggs or young exposed. Birds that quickly flush 
from nests may accidentally break eggs or kick eggs or young from their 
nests. Mammal adults and young may become separated when they panic and 
flee. Leaving the young exposed also makes them vulnerable to predators. 

Numerous studies have addressed the effects of aircraft overflights on the 
breeding success of ungulates such as caribou and Dall sheep. Generally, 
overflights have not been shown to cause adults and young to separate. Yet 
one study attributed Caribou calf mortalities to frequent low-level military 
aircraft overflights (Harrington and Veitch 1992). This study compared calf 
mortality rates in groups that were exposed to overflights with rates in 
groups that were not exposed. Mortality rates were significandy higher in the 
exposed group. The researchers hypothesized that milk release was inhibited 
in caribou mothers that were disturbed by the overflights, and so young 
became malnourished. As this example suggests, calves might not die direcdy 
from overflights, and so mortalities cannot be detected unless studies are 
designed to compare rates of survival between calf groups that are and are 
not exposed to overflights. Numerous studies have reported that overflights 
do not affect survivorship in young, yet they do not compare survivorship of 
young that were and were not subjected to overflights. This example 
demonstrates how complex cause and effect relationships can be between 
disturbance and effects. It also shows that casual observations of how animals 
respond to overflights do not necessarily reveal ultimate consequences. 

Waterfowl and seabirds nesting on national wildlife refuges are commonly 
exposed to both military and private aircraft overflights. Whether or not 
overflights have indirect effects on breeding success depends on the 
circumstances and types of behavioral responses of the adult birds: whether 
or not they flush from their nests, whether the exposed nests are vulnerable 
to predators, proximity of other nests (some birds nesting close together 
tend to fight after a disturbance, resulting in egg breakage), and physical 
characteristics of nests and of the adults. Many refuge managers have 
reported that birds flush from nests in response to overflights (Gladwin et al. 
1987, USFWS 1993). This is considered a problem because of the potential 
for losses of eggs and young. Gulls, cormorants, and murres, lor example, 
kick eggs from nests when they flush during disturbance, and eggs are lost, 
broken or eaten by predators. These events have been documented to occur 
on several national wildlife refuges (USFWS 1993). Some species, such as 
tundra swans and pelicans, apparendy abandon nests due to chronic 



114 



5.4 Indirect Effects of Disturbance from Overflights, and Consequences for Animals 



disturbance from overflights (Gladwin et al. 1987, USFWS 1993). Leaving 
eggs exposed to sun or rain also jeopardizes their survival. 

Several studies have been conducted on nesting birds and their responses to 
overflights. Both American white pelicans and brown pelicans appear to be 
particularly susceptible to disturbance. Pelican biologists have discovered that 
low-flying aircraft can contribute to dramatic reductions in survivorship of 
young and in overall productivity of a nesting colony (Bunnell et al. 1 98 1 , 
Gladwin et al. 1987). Some species, when subjected to overflights during 
studies, did not flush from nests and so losses did not occur. Such species 
include: trumpeter swans (Henson and Grant 1991), catde egrets, 
double-crested cormorants, great blue herons, great egrets, and white ibises 
(Black et al. 1984). Others did flush from nests but did not tend to kick eggs 
from them and so no losses occurred. These species include: great egrets, 
snowy egrets, and tricolored herons (Kushlan 1979). These species have only 
been tested for responses to overflights during the studies referenced above. 
Therefore it is not known whether more intense stimuli such as aircraft 
flying at lower altitudes might cause more panic and subsequent egg or chick 
losses. 

Disrupted patterns of parental attendance to eggs or chicks is also a concern. 
Although this phenomenon has been noted on a local scale, it has not as yet 
been widely linked to reproductive losses at a regional or national scale. One 
study, however, suggests that supersonic overflights might cause large-scale 
losses. In 1969 low-altitude supersonic aircraft overflights of the Dry 
Tortugas during the nesting season were suspected to cause a massive 
hatching failure for sooty terns (Austin et al. 1970). This incident is widely 
cited as one of severe disturbance, though the cause and effect relationship 
cannot be proven. Studies of some nesting birds that respond to less intense 
(i.e., subsonic) overflights generally return to the nest to resume incubation 
after the aircraft has passed. 

Raptors (birds of prey) have also been monitored for signs of disturbance 
from overflights during the breeding season. Occasionally, raptors are 
disturbed by aircraft enough to respond by flushing from their perches or 
nests. One pair of bald eagles at Cross Creeks National Wildlife Refuge in 
Georgia reportedly abandoned nesting activities altogether and left the area 
after repeated overflights by a military helicopter (Gladdys 1983). On the 
other hand, once eggs are laid, raptors may be less inclined to abandon nests. 
Ellis et al. (1991) reported that nest abandonment and nest failures through 
predation, exposure of the eggs, or egg losses did not occur during a study of 
raptor responses to low-flying military jet aircraft. Although conclusions 
cannot be made from these two reports alone, the evidence suggests that the 
seasonal timing of overflights may be an important factor in the outcome of 
disturbance. 



115 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



5.4.3 Energy Losses 

Panic reactions and escape responses to overflights can be energetically 
"expensive" to animals for two reasons. First, feeding animals nearly always 
stop ingesting food when disturbed, which means a decrease in energy 
intake. Second, disturbed animals usually run or otherwise move away from 
the aircraft, thus increasing their energy expenditure. Running can increase 
an ungulate's metabolism twenty-fold over the normal resting rate (Mattfeld 
1974). Hence frequent disturbance imposes a burden on the energy and 
nutrient supply for animals (Geist 1978), which can compromise growth and 
reproduction. 

There is a particular concern that birds may suffer from energy losses due to 
chronic disturbance, especially during periods when increasing and storing 
energy reserves is critical for survival. During winter, the energetic costs of 
daily activities, such as keeping warm and feeding, mean that animals can 
spare little extra energy. During other seasons, such as the staging period or 
breeding season, large net gains of energy are required for migration and/or 
raising young. For example, the high energy requirements of ducks and geese 
during the molting season may not be met if these birds continuously swim, 
dive, or run from aircraft (Gollop et al. 1914b). Migrating birds such as snow 
geese may be vulnerable to disturbance during the staging season, when 
energy accumulation must be great enough to prepare for the high energetic 
demands of migration. Salter and Davis (1974) documented snow geese 
flushing repeatedly in response to overflights during the staging period just 
prior to their migration. The amount of time available for and the limits to 
compensatory feeding, or making up for lost time, are unknown. When 
animals are already feeding for a significant portion of the day, the 
opportunity for compensatory feeding is probably limited. 

There have been four notable attempts to examine the effects of aircraft 
disturbance on bioenergetics of animals. Three were conducted on birds 
during the staging season; two of these used snow geese as models, (Davis 
and Wisley 1974, Belanger and Bedard 1989a,i), the other used brant 
(Ward and Stehn 1989). All three of these studies found that, in the 
presence of frequent overflights, birds lost feeding time because they stopped 
feeding to react to the aircraft. Belanger and Bedard observed snow geese 
and their responses to human-induced disturbance, including aircraft, on 
their staging grounds over three years. They found that snow geese both 
increased their energy expenditure and decreased energy intake in response 
to aircraft disturbance. They found that, if disturbance occurred at a rate of 
1 .46 per hour (as it did during their study), birds could compensate for 
energy losses by feeding at night, but if they flushed from disturbance and 
did not return to feeding areas, they would have to feed during 32 percent of 
the night — a significant time commitment. They also found that birds did 



116 



5.4 Indirect Effects of Disturbance from Overflights, and Consequences for Animals 



not compensate during the day by increasing the rate at which they fed after 
disturbance. These researchers concluded that man-induced disturbance can 
have significant energetic consequences for staging snow geese. 

The amount of food that bighorn sheep ingest while grazing in the presence 
and absence of tourist helicopters was investigated in Grand Canyon 
National Park (Stockwell and Bateman 1987). Sheep spent 14-42 percent 
less time (depending on the season) foraging in the presence of helicopters. 
In addition, sheep increased the number of walking steps while foraging by 
50 percent. This study suggests that the increase in energy expended, 
coupled with a decrease in energy consumed, might contribute to an energy 
deficit for animals when disturbance is chronic. Disturbance has been 
documented as influencing pronghorn foraging also (Berger et al. 1983). 

5.4.4 Habitat Avoidance and Abandonment 

Many wildlife biologists are concerned that the disturbance from overflights 
could cause sensitive animals to abandon their habitats. This subject has 
drawn attention because the consequences of habitat abandonment can be 
serious, particularly for species whose high-quality habitat is already scarce. 
Observations suggest that some animals do abandon their habitats in 
response to overflights, and some do not. This difference may be due to 
differences in the sensitivities of individual animals. On the other hand it 
may be a factor of different levels of exposure to aircraft during these studies 
(different flight altitudes, aircraft types, and flight frequencies). Two studies 
found that caribou did not abandon areas in response to small aircraft 
overflights (Bergerud 1963, Harrington and Veitch 1991), and one found 
that they did (Gunn et al. 1985). Grizzly bears (McCourt et al. 1974), 
mountain sheep (Krausman and Hervert 1983, Bleich et al. 1990), and 
mountain goats (Chadwick 1973, Ballard 1975) all have been noted to 
abandon areas in response to small aircraft overflights, even when overflights 
were infrequent. It is not known how many other species avoid areas used by 
aircraft. 

Waterfowl biologists and national wildlife refuge managers have expressed 
concern about how waterfowl use of open water and emergent wedand 
habitats is disrupted by aircraft overflights. Overflights have been reported to 
cause disturbance at dozens of wildlife refuges in 30 states (Gladwin et al. 
1987). Most often, waterfowl flush from lakes and fly away, but return once 
the noise levels in the area return to ambient. On the other hand, several 
refuges have reported that some waterfowl species have been completely 
driven off by frequent aircraft activity. Belanger and Bedard's (\9S9a,b) study 
on snow geese energetics and disturbance showed a significant drop — 50 
percent in the number of geese using feeding grounds on days following 
aircraft disturbance. Waterfowl using lakes in Canada were displaced for 



117 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



several days when disturbed by light aircraft overflights (Schweinsburg et al. 
1914b). Wintering sandhill cranes leave feeding and loafing areas (resting 
areas) for extended periods when low-altitude overflights take place over 
Cibola and Imperial Wildlife Refuges (USFWS 1993). Wood storks may also 
abandon habitat in response to overflights (USFWS 1993). Observations by 
refuge biologists suggest that the endangered Palila Bird in Hawaii 
underutilizes a sizable portion of its critical habitat because of low-altitude 
military aircraft overflights (Gladwin et al. 1987). It is not currendy known 
how the use of ponds, lakes and wedands in national parks is affected by 
overflights. 

Wildlife refuge and national park managers are also concerned because game 
animals are sometimes chased from parks and refuges into areas where they 
may be hunted. This has been documented in several refuges and one 
national park (USFWS 1993). This harassment is suspected to be 
intentional; hunters are gaining access to animals which are usually protected. 

Aircraft activities appear to have varying impacts on raptors' use of habitat. 
In general, raptors are sensitive to the activities of people, although 
species-specific differences are evident. Raptors have been documented to 
abandon both wintering and breeding habitats as a result of human 
disturbance (Stalmaster and Newman 1978, White and Thurovv 1985). Ellis 
et al. (1991) found little evidence, however, that raptors abandon habitat in 
response to aircraft overflights. 



CONCLUSION 5.3: 

Researchers have documented 

some indirect effects for some 

species and individuals, such as 

eggs kicked from nests when 

birds flush in response to 

overflights, loss of feeding due 

to overflight disturbance, 

abandonment of habitat in 

response to overflights. Other 

studies have found no such 

effects for some species and 

individuals. 



5.4.5 Potential Bird Strike Hazards 

There is some concern over potential aircraft collisions with airborne birds 
among national wildlife refuge managers. Collisions are a misfortune for both 
birds and pilots. Bird strikes have cost the lives of many pilots and/or 
damaged aircraft. Military aircraft are most vulnerable to bird strikes since 
they fly at low altitudes and high speeds. The US Air Force reports 3,500 
bird strikes annually (Spectrum Bird Aircraft Strike Hazard Team 1994). 
The Air Force continues to develop methodologies for avoiding 
concentrations of birds, in order to reduce this frequency. The FAA further 
recognizes that large concentrations of migratory birds are a safety hazard to 
pilots. 



4. Memorandum dated March 7, I 994Jrom Supenntendent. Olympic National Park, to Acting Associate Director, Operations. National Park Service. 



118 



5.5 Factors that Influence Animal Responses fo Aircraft 



5.5 Factors that Influence Animal Responses to 
Aircraft 

It is clear from numerous studies that differences in animal responses to 
aircraft do not depend solely upon the species in question. Many other 
factors contribute to the responses to overflights, some having to do with the 
animal and its particular environment and some having to do with the 
aircraft stimulus itself. 

5.5. 1 How Animals Perceive the Aircraft Stimulus 

An animal's sensory perception of aircraft activity depends, in part, on the 
physical features of its environment, as well as on its own physiological 
attributes. Some habitats enhance stimuli associated with aircraft overflights. 
For example, high canyon walls have the effect of amplifying and repeating 
(echoing) aircraft sound, and yet they can also obstruct the aircraft from 
view. The sound and visual stimuli associated with aircraft have different 
effects in an open desert than in a forest where trees can obscure the sight 
and may reduce the sound of aircraft. A further consideration is the animal's 
sensitivity to different types of stimuli, which depends on physical limitations 
of the senses. Some animals can clearly see aircraft when they are barely 
visible to others, and the range of frequencies of sound that can be detected 
varies gready from species to species. 

One relationship between aircraft and animals is clear: the closer the 
aircraft, the greater the probability that an animal will respond, and the 
greater the response. Unfortunately, there is no particular overflight altitude 
at which all animals are or are not disturbed. Even within a species, no 
particular altitude can be identified as causing a sudden increase in 
disturbance, because so many other factors influence disturbance. Notably, 
some studies have shown that animals react in the same manner regardless of 
altitude (e.g., Lenarz 1974, McCourt et al. 1974). It is unlikely that one 
overflight altitude exists that is sufficient for avoiding disturbance to all 
animals while not necessarily imposing undue restrictions on pilots. For 
instance, a 5,000 foot minimum altitude may avoid disturbance to all 
species, but may not be necessary at all times. Researchers have reported 
disturbances to walruses by helicopters flying as far away as 4,270 feet (Salter 
1979). Grizzly bears run away from aircraft flying at altitudes as high as 
3,000 feet. Few other animals have been tested for responses to aircraft at 
altitudes this great, though many show disturbance from aircraft at lower 
altitudes. 



119 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



5.5.2 Aircraft Sound and Animal Hearing 

It is apparent that animals can be disturbed by either the sight or sound of 
aircraft (McCullough 1969, Snyder et al. 1978, Ward and Stehn 1989, 
Brown 1990). The relative importance of each stimulus is not known, and 
may depend on the species in question. Both birds and mammals respond to 
the sound of aircraft before it is visible, yet they also tend to track aircraft 
visually as they pass overhead (McCullough 1969, Snyder et al. 1978, Brown 
1990). 

Aircraft sound is broadband, containing sound energy over a wide frequency 
range, rather than a pure tone. There is some evidence that the 
high-frequency whine of some turbine-powered helicopters is less disturbing 
to raptors than the low-frequency sound of piston-engine helicopters (White 
and Sherrod 1973). Other than this, little is known about how the 
frequencies of aircraft sound influence animal responses. Sound levels at 
which animals show strong negative responses in the wild generally have not 
been determined. 

Helicopters apparendy disturb some animals more than other types of 
aircraft. Comparisons of how animals respond to helicopters versus other 
aircraft types have shown that animals respond more strongly to helicopters. 
For example, caribou ran longer and farther in response to helicopter 
overflights than they did in response to low-altitude overflights by military 
jets during a study in the Yukon (Harrington and Veitch 1991). Ward and 
Stehn (1989) also noted that greater percentages of brant responded to 
helicopters than to fixed-wing aircraft in Alaska. Colonially-breeding marine 
birds also generally flushed when helicopters flew over them at 1 ,000 feet 
above ground level (AGL), while light, fixed-wing aircraft could pass over at 
500 feet AGL before generating a similar response (Gollop et al. 19746). In 
addition to their engine and "rotor-wash" sound, helicopter flight patterns 
may contribute to disturbance. Brant (Henry 1980), reindeer (Ericson 
1972), caribou (Calef and Lortie 1973, Miller and Gunn 1977), pronghorn, 
elk, bighorn sheep (Workman et al. 1992a, 19926, 1992c), and Dall sheep 
(Andersen 1971) all have been documented to show a more extreme panic 
response when helicopters fly slowly or hover over animals. 

Sudden aircraft approaches that cause surprise may also influence responses. 
Raptors, for example, panicked and exhibited frantic escape behavior when 
helicopters appeared from over the tops of cliffs, but did not do so when 
helicopters could be seen approaching from a distance (White and Sherrod 
1973). Hence topography should be taken into consideration when 
predicting animal responses to overflights. 



120 



5.5 Factors that Influence Animal Responses to Aircraft 



5.5.3 Increased Tolerance to Overflights 

In some cases, animals may develop an increased tolerance to frequent 
overflights. This has been demonstrated by correlating changes in behavior 
with sequences of overflights. Other studies have compared reactions of 
animals having a history of exposure to aircraft with those that were naive. In 
many cases, experienced animals were more tolerant of aircraft, showing less 
extreme responses than naive animals. 

For animals to become desensitized to sound, there must be consistent 
stimuli (Borg 1979); frequent, predictable overflights, such as those at major 
airports, are more likely to promote tolerance than occasional ones. Several 
studies suggest that animals might not become tolerant of infrequent aircraft 
activity. Colonially-breeding wading birds in Florida, for example, never 
adapted to infrequent low-altitude military flight activities conducted over 
two breeding seasons (Black et al. 1984). It is not known just how frequendy 
a stimulus must occur in order for an animal to become desensitized to it, 
though it probably depends upon the species in question, as well as other 
factors. 

It is important to note that some studies do not support the idea that 
animals' tolerances of aircraft overflights increase with exposure, even when 
overflights have been frequent. For example, brant, emperor geese, and 
Canada geese in Alaska (Ward and Stehn 1989) exhibited alert and flight 
behavior in response to aircraft activity, despite previous exposure for several 
seasons. Harding and Nagy (1976) noted that grizzly bears also never became 
tolerant of aircraft, despite very frequent exposure. 

The degree of disturbance to which animals can habituate is probably 
limited. Evidence suggests that aircraft activities that cause mild responses 
may become tolerated more so than those that cause panic. This has been 
demonstrated in reindeer (Ericson 1972), Dall sheep (Summerfield and 
Klein 1974), and herring gulls (Burger 1981). Also, while some species have 
the ability to become tolerant, others may not. For example, whooping 
cranes appeared to have become tolerant of light aircraft activity on Aransas 
National Wildlife Refuge in Texas, but sandhill cranes had not (Gladwin et 
al. 1987). 



CONCLUSION 5.4: 

Factors thai can influence 
animal responses include 
distance to the aircraft, aircraft 
type, suddenness of aircraft 
appearance and frequency of 
overflights. Closer aircraft 
generally are more likely to 
produce a response, though no 
minimum distance that 
produces no effect has been 
found, the responses being 
species dependent. Some 
tolerance for overflights has 
been observed when flights are 
frequent or regular, but not 
among all species. 



121 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



CONCLUSION 5.5: 

The type of animal activity 

affects response to overflights. 

Whether an animal is feeding, 

resting, caring for young, etc., 

can affect how it responds to 

an overflight. 



5.6 Biotic Factors that Influence Animal Responses 
to Aircraft 

While sound levels and aircraft proximity to animals are probably the most 
important factors affecting the levels and types of responses elicited, an 
animal's immediate activities are also important. Animals show different 
levels of response to overflights depending in part on whether they are 
traveling, feeding, resting, or attending young. Habitat features may also 
influence the degree to which animals react to overflights. For example, 
bighorn sheep in the San Andreas National Wildlife Refuge appeared more at 
ease in response to helicopters when in open terrain where they could 
escape more easily (Kiger 1970). 

An animal's seasonal activities such as reproducing or hibernating influence 
how they respond to overflights as well. Consequendy, during some seasons, 
animals may be more reactive than during other seasons. Slight seasonal 
differences in responses to overflights have Deen noted in reindeer (Slaney 
and Co. 1974), bighorn sheep (Stockwell and Bateman 1987), and caribou 
(Klein 1973, McCourt and Horstman 1974, Jakimchuk et al. 1974, Calefet 
al. 1976). Generalizations cannot be made across species correlating specific 
seasons with greater reactions. 

At present, general relationships between external factors and animal 
responses are unclear because other variables have not been held constant 
during studies. In other words, to determine how habitat type (for example) 
influences responses, all other factors such as group size, season, etc. must be 
held constant so that habitat differences alone can be compared. Stronger 
patterns should emerge once more controlled studies are conducted. The 
existence of many variable factors may explain inconsistencies between 
reports of species-specific responses to overflights. Clearly, whether an 
animal (or group of animals) responds to aircraft overflights depends on 
many factors, and those mentioned here constitute only a partial list. 
Therefore, when attempting to assess the possible impacts of proposed or 
existing low-altitude aircraft operations on wildlife, it is essential to keep in 
mind that each situation is unique and must be evaluated accordingly. 
Figures 5.1 and 5.2 summarize some of the influential factors associated widi 
aircraft overflights and animals that have been addressed. 



122 



5.6 Biof/c Factors that Influence Animal Responses to Aircraft 



INFLUENCING FACTORS 



Previous experience with aircraft 

Sex & age 

Season 

Habitat 

Current Activity 

Life-cycle state (breeding, migrating, etc.) 



ANIMAL 



DIRECT EFFECTS 



Behavioral reponse 



INDIRECT EFFECTS 



none 

stop current activity 

look up, change body 

position 

leave area (temporary or accidental injuries 

permanent) 



no effect 

energy losses 

altered patterns of care to young 

habitat avoidance 



Physiological reponse 

no effect 
hearing loss 
increased heart rate 
adrenaline release 



none 

increased susceptibility to disease 

increased vulnerability to predators 



ULTIMATE 
CONSEQUENCES 



none 

reduced survivorship 
reprodctive losses 
habitat loss 



Figure 5. 1 : Animal Responses to Low-Altitude Aircraft Overflights 




altitude 



flight frequency 
flight speed 
flight pattern 




terrain type 

season 

habitat features 



Figure 5.2: External Factors that Influence Animal Responses to Overflights 



123 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



5.7 Problems with Detecting Long-Term Effects of 
Aircraft Disturbance 



CONCLUSION 5.6: 

The long-term effects of 

overflights on wildlife have not 

been determined, and are 

unlikely to be investigated 

because of the magnitude of 

the effort required. Occasional 

use of aircraft to survey animals 

is unlikely to cause harm. 



While short-term responses are easily documented, long-term responses are 
more difficult to verify. This is due both to the limitations of ecological 
research and to the nature ot long-term responses. Long-term responses that 
might occur include permanent changes in habitat use, increased mortality of 
birds during migration (due to lower weight gains during staging, as 
described previously), or population effects due to reduced reproductive 
success (due to egg losses, for example). Assigning a cause and effect 
relationship between overflight disturbance and these types of phenomena is 
difficult because there are so many other variables that also cause them. It is 
very difficult to quantify small decreases in the survivorship of young that are 
direcdy attributable to overflights, because predators, weather, food 
availability, and adult skills all affect survivorship as well. For example, several 
studies have examined overall survivorship of young across a season by 
comparing young subjected to overflights with control animals and have 
concluded that overflights have little effect. However, closer examination has 
revealed that mortality rates increased during the specific periods of 
overflights, though these increases were not detectable by the end of the 
season (e.g., Harrington and Veitch 1992). Other long-term effects are 
difficult to correlate with overflights because they occur during a time or in a 
place not immediately associated with the overflights, such as migrating birds 
that die enroute to their destination after energy losses at feeding grounds. 

Long-term effects are difficult to detect also because they may occur 
infrequendy. This is due, in part, to the fact that most studies are 
short-term, making documentation of infrequent events unlikely. With the 
exception of an eight-year study of white pelicans (Bunnell et al. 1981), too 
litde time has been spent assessing long-term effects. 

Many biologists have published reports on the effects of the use of aircraft to 
survey animals. In most cases, overflights do no harm (Carrier and Melquist 
1976, Kushlan 1979) because normal behavior is interrupted only briefly. In 
addition, the surveys are conducted only once or twice per season, and 
generally they are avoided during poor weather, when stressing an animal 
could result in harm, and during parts of the breeding season, when the 
consequences of disturbance might be compounded (White and Sherrod 
1973, Poole 1989). Hence the argument that biologists themselves make 
overflights of animals should not be used to suggest that overflights do not 
cause disturbance. 



124 



5.8 Overflight Impacts on Endangered Species 



5.8 Overflight Impacts on Endangered Species 



There are 98 species on national park lands that have been identified as 
threatened or endangered. Of these, 36 are bird and 29 are mammal species. 
The impacts on threatened or endangered species From overflights is largely 
unknown. Of all threatened or endangered species Federally listed in the 
United States, there is information regarding responses to overflights only 
for the grizzly bear, sonoran pronghorn, peregrine falcon, bald eagle, and 
everglades kite. None of these species have been studied enough to 
differentiate between aircraft activities that do and do not cause harm. 
However, observations do indicate that some species are susceptible to 
disturbance and subsequent harm. The grizzly bear, for example, has been 
noted to panic and flee areas from overflights in nearly all cases where they 
have been observed (see Table 1). Biologists recognize that impacts may 
occur. Wildlife refuge managers have cited concern for many threatened or 
endangered species regarding impacts from overflights, including wood 
storks, Hawaiian geese, marbled murrelets, bald eagles, peregrine falcons, 
masked bobwhite quails, Stellar sea lions and least terns (USFVVS 1993). In 
Washington State, USFWS is developing recovery plans for both the marbled 
murrelet and northern spotted owl which include 2,000-foot minimum 
flight restrictions over feeding grounds and nesting sites for these birds . 

Many threatened or endangered species have achieved their special status 
due to habitat loss from development and general human encroachment. 
They are species for which habitat is limited; their natural histories prevent 
them from using any but specific habitat types. For this reason, it is 
important that overflights not cause further habitat loss to these species, 
since they cannot simply "relocate". 

Whether or not a taking of a threatened or endangered species from Federal 
action occurs from overflights may be an area for additional research. It 
would be prudent for Federal agencies to take an active approach to 
evaluating this, rather than letting the decision lie with the courts. Studying 
threatened and endangered species and their responses to overflights is 
within the purview of the law so long as research enhances the survival of the 
species. However, some have expressed concern for the idea of subjecting 
animals to overflights and monitoring their responses if indeed those 
responses suggest that damage is occurring. 



CONCLUSION 5.7: 

Ninety-eight threatened or 
endangered species inhabit 
units of the National Park 
System. Their responses to 
overflights are largely 
undocumented, but Federal 
agencies may nevertheless be 
held responsible for impacts 
related to overflights. 



5. Memorandum dated March 7, I 994Jrom Superintendent, Olympic National Park, to Acting Associate Director, Operations, National Park Service. 



125 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



5.9 Overflight Impacts on National Park Animals 

Disturbance levels and consequent impacts to animals living on national park 
lands have been anecdotally reported but not quantified. Several NPS 
superintendents have prepared reports on the subject which can be used as 
indicators of the types of problems some parks are having. Yet the degree to 
which these problems are occurring in other parks cannot be measured 
without a comprehensive survey. 

Reports of park disturbance to animals from overflights exemplify the 
general points described earlier: 1) Animals have been noted to modify their 
behavior in response to overflights in parks, and 2) the consequences of this 
disturbance can only be inferred in the absence of long-term studies. At 
Hawaii Volcanoes National Park, the endangered Hawaiian (Nene) goose has 
been seen flushing from feeding and socializing areas after tour helicopters 
passed overhead . Aircraft also alter normal feeding and socializing habits in 
response to frequent overflights. The consequences of altering social 
behaviors and time and energy budgets of animals have not been identified. 
Forest birds at this park also stop calling or flee from local habitat, as noted 
by biologists monitoring songbird behavior. Biologists speculate that bird 
behavior is modified because their calls are interrupted, hence territories 
cannot be properly delineated. Feeding is also interrupted, and other critical 
activities cannot be consummated when birds are disturbed by overflights. 

At Congaree Swamp National Monument, bald eagles and osprey are 
believed to avoid habitats they would otherwise use because of overflights by 
military jets and helicopters. Similar impacts to raptors have been reported 
from Glacier National Park. There, overflights are suspected of disrupting 
nesting and foraging activities of bald eagles, golden eagles and falcons. 
Biologists are concerned about possible impacts to raptors that use corridors 

o 

through the park for migration . Colonial seabirds have been seen flushing in 

9 
response to overflights in Olympic National Park as well . Other birds diat 

may suffer harm from overflights in this park include the bald eagle, 

peregrine falcon, northern spotted owl, and marbled murrelet. These are all 

Federally-listed species. 

Mammals are also disturbed by overflights in parks. Over 80 percent of 
grizzly bears observed in remote areas of Glacier National Park showed a 



6. Memorandum dated March 7, I 994 from Superintendent, Hawaii Volcanoes National Park, to Acting Associate Director, National Park Service. 

7. Pers. comm., Robert McDaniel, Superintendent, Congaree Swamp National Monument, to D. Gladwin, Sterna Fuscata Inc. 1994. 

8. Memorandum dated March 7, / 994jrom Superintendent, Glacier National Park, to Acting Associate Director, Operations, National Park Semce. 

9. Memorandum dated March 7, 1994 from Superintendent, Olympic National Park, to Acting Associate Director, Operations, National Park Service. 



126 



5. 10 Development of Impact Criteria 



"strong" reaction to helicopters, according to studies in the park from 
1982-1986. 

Aircraft disturbing park animals include both military and civilian fixed-wing 
aircraft and helicopters. Helicopter tours for the public are most often cited 
as causing problems for wildlife. Most problems occur when aircraft fly at 
low altitudes such as 500 feet AGL. Helicopter tour operations are frequent 
in some parks; Glacier National Park reports 1 per day, and Hawaii 
Volcanoes National Park reports 60-80 per day. Hence cumulative effects of 
disturbance are likely, as animals are chronically interrupted from important 
life-maintenance activities. 

Several efforts to solve disturbance problems have been initiated by park 
personnel in recent years. Monitoring low-level overflights and maintaining 
statistics at Congaree Swamp National Park have helped to quantify the 
frequency of problems. At Olympic National Park, the staff are cooperating 
with the USFWS refuge staff and the endangered species field office in 
documenting and reporting aircraft harassment of seabird colonies. At 
Glacier National Park, employees are trained to identify aircraft and estimate 
altitude. A strict plan is in place there for the use of the park's own aircraft. 
Parks have also discussed problems with aviation proponents. Meetings with 
tour operators, FAA, and military personnel have been somewhat successful, 
though problems do not always cease. For example, Congaree Swamp 
national park managers note that, although military personnel are receptive 
to cooperation in avoiding disturbance, no efforts have been made by the 
military to address problems themselves or to offer mitigation strategies. At 
Hawaii Volcanoes National Park, staff have been negotiating a voluntary 
agreement with the helicopter operators association, with assistance from the 
FAA. 

Park superintendents have an interest in addressing cumulative effects of 
aircraft disturbance on wildlife. They also support continued efforts to work 
with the military and civilian aircraft operators to develop mutually agreeable 
solutions. Preparing educational material on the sensitivity of wildlife and 
natural areas has been suggested as a means of reducing disturbance. 



5.10 Development of Impact Criteria 

Studies to-date have verified that physiological and behavioral responses by 
wildlife to low-flying aircraft do occur. The nature of these responses 
suggests that at least some animals suffer other consequences. The studies by 
Stockwell et al. (1991) and Belanger and Bedard (I989a,b) provide 
compelling evidence that energy losses and habitat avoidance are occurring in 
response to overflights. Unfortunately, these studies cannot be used to infer 



CONCLUSION 5.8: 

In general, reports from 
national park about the effects 
of overflights on wildlife tend to 
mirror the points made earlier 
in this chapter: animals have 
been observed to modify their 
behavior in response to 
overflights, but without long 
term study, the consequences of 
such modifications can only be 
inferred. 



127 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



damages in other species or from other overflight regimes. Only a handful of 
the many species that inhabit national parks have been studied for responses 
to overflights. It is very likely that there are park species that are susceptible 
to disturbance that have never been studied. There is also little information 
suggesting how flight patterns, frequencies and altitudes affect any species, 
•other than the broad generalizations described earlier. Data to support the 
occurrence of damage in a variety of situations would require many years of 
extensive and cosdy research. 

It is also not possible to evaluate the after-effects of overflights because in 
most cases, animal responses fall across a spectrum so that the question of 
whether or not a disturbance occurs cannot be answered with a yes or no. 
For example, an overflight generally causes some animals to panic, some to 
be mildly disturbed, and some animals to ignore the aircraft. At a lower 
altitude, the overflight causes more to panic and fewer to be mildly 
disturbed. At what degree of disturbance in what percentage of animals 
should overflights be considered detrimental or otherwise unacceptable? At 
present, these questions have only largely subjective answers. 

Defining impacts according to some specific, measurable criteria is a useful 
first step towards developing a policy. There is no consensus in public or 
scientific communities regarding impact definition. The following categories 
of impacts are adapted in part from a matrix of definitions developed by Oak 
Ridge National Laboratory staff members Roger Kroodsma and Warren 
Webb in cooperation with the U.S. Air Force (Braid 1992). They are meant 
to help agencies in determining the severity of impacts. In these definitions, 
"species of concern" include Federally- or state-listed threatened, 
endangered, and candidate species, species of local economic importance, or 
species of particular concern to conservation or other interest groups. This 
definition can be expanded to include any species that is known to be 
susceptible to disturbance. "Habitat" is used to refer to the physical 
landscape and its ecosystem components that are subjected to overflights. 

Negligible Impacts 

■ No species of concern are present and~no or minor impacts on any 
species are expected. 

■ Minor impacts that do occur have no secondary (long-term or 
population) effects. 

Low Impacts 

■ Non-breeding animals of concern are present in low numbers. 

■ Habitat is not critical for survival and not limited to the area targeted 
for overflight use; other habitat meeting the requirements of animals 
of concern is found nearby and is already used by those species. 



128 



5.10 Development of Impact Criteria 



Occasional fright responses are expected, but without interference 
with feeding, reproduction, or other activities necessary for survival. 
No serious concerns are expressed by state or federal fish and 
wildlife officials. 



Moderate Impacts 



■ Breeding animals of concern are present, and/or animals are present 
during particularly vulnerable life-stages such as migration or winter 
(depends upon the species in question). 

■ Mortality or interference with activities necessary to survival are 
expected on an occasional basis. 

■ Mortality and interference are not expected to threaten the 
continued existence of the species in the area. State and federal 
officials express some concern. 

High Impacts 

■ Breeding individuals are present in relatively high numbers, and/or 
animals are present during particularly vulnerable life-stages. 

■ Habitat targeted for overflights has a history of use by the species 
during critical periods, and this habitat is somewhat limited to the 
area targeted for overflight use; animals cannot go elsewhere to avoid 
impacts (animals can rarely "relocate" except temporarily). 

■ Mortality or other effects (injury, physiological stress, effects on 
reproduction and young-raising) are expected on a regular basis. 
These effects could threaten the continued survival of the species. 

■ State and federal wildlife officials express serious concern. 

This evaluation process relies on the opinions of wildlife managers and 
researchers. In general, members of the scientific community agree that 
damage to animals should not need to be proven before impacts are 
considered likely. In the conclusion of the majority of studies, researchers 
caution that, though they cannot prove that impacts occur, overflights that 
cause disturbances should be avoided. 

In defining what level of disturbance to park animals by overflights is 
unacceptable, the NPS must rely on less than complete information. It is 
clear that disturbances can result as direct and indirect effects, and that 
consequences may affect survivorship. Until more information is available, it 
is recommended that the NPS use the levels of impact listed to "trigger" 
actions to eliminate or reduce such impacts. In general, the NPS would 
regard situations consistent with "low impacts" to warrant monitoring, while 
situations that represent "moderate impacts" or "high impacts" would 
require pursuit of solutions. 



129 



REPORT TO CONGRESS: Effects of Overflights on Wildlife 



5.11 Summary 

A wide range of impacts (disturbances) to wildlife due to aircraft overflights 
have been reported in the literature. There are many reports of behavioral 
responses in animals, these responses are highly variable depending on the 
type of study, the species under consideration, spatial and temporal 
parameters, and other broad ecosystem characteristics. 

Indirect effects on wildlife such as accidental injury, energy losses and 
impacts to offspring survival have been documented. Current literature 
supports the argument that aircraft overflights negatively impact wildlife 
populations. However, the significance of such impacts is not clear. 
Additional studies are still needed to better assist land managers in 
substantiating the effects on population subgroups. 

It is certain that some impacts do occur under certain circumstances and 
that it is a NPS priority to protect wildlife, especially threatened and 
endangered species, whenever a probable impact exists or is expected. 
Hence, a series of .conditions, applicable system-wide, have been listed that 
can be used to define general levels of impacts. Working with these 
guidelines at specific parks will lead to setting of priorities, both for possible 
alteration of overflight times, locations and numbers, and for identification 
of further research needs. 



130 



6&*pf6 



6 



EFFECTS OF OVERFLIGHTS ON VISITOR 
ENJOYMENT 



6. 1 Introduction 

Public Law 1 00-9 1 directs the Secretary of the Interior to study the effects 
of aircraft overflights at no fewer than ten units of the National Park System, 
and to provide information at each unit regarding 

"... the impairment of visitor enjoyment associated with flights 
over such units of the National Park System. " 

This chapter presents the results of two studies that were conducted in 
response to this requirement and that serve to identify the effects on visitors 
and also to provide a basis for using visitor reactions, as one measure among 
others, to identify, analyze and mitigate aircraft overflight sound produced 
impacts at units of the National Park System. 

The two studies that serve as the basis for most of the analysis presented in 
this chapter are the Visitor Survey (McDonald et al. 1994) and the 
Dose-Response Study (Anderson et al. 1993). The Visitor Survey consists of 
two surveys of visitors: a visitor intercept survey conducted at exits to parks 
as visitors were departing, and a mail survey sent to a sub-group of these 
visitors. The Dose-Response Study included simultaneous sound level 
measurements and visitor interviews at specific sites which are overflown by 
aircraft on a regular basis. The Visitor Survey was designed to provide 
National Park System-wide estimates of visitor impacts, but the results also 
provide valuable information on the variation in effects from park to park. 



- 131 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



The Dose-Response Study examines visitor reactions to overflights of 
specific park locations and provides a quantitative relationship between 
aircraft sound level and visitors' reactions to these sound levels. The sections 
of this chapter examine in succession the effects on visitors system-wide, at 
specific parks, and at specific sites within parks. These effects, and in 
particular the results of the specific site Dose-Response Study, are then used 
as the basis for a process of identification, analysis and mitigation of 
overflight produced visitor impacts. 

Understanding Visitor Enjoyment 

In order to understand the following shifts of analysis from park system to 
individual parks to specific sites, it is necessary to understand how visitors 
report enjoyment and how the NPS views its mandate to provide for visitor 
enjoyment. In a recreational setting, visitor reports of enjoyment (or visitor 
satisfaction, as it is often termed in the literature) have two important 
qualities: 1) reports of satisfaction and dissatisfaction depend upon how 
specifically a visitor is questioned about an experience; 2) satisfaction cannot 
really be examined with a single measure, but consists of multiple 
satisfactions. First, previous work has shown that people evaluate their 
reactions to an event more reliably to the extent that they are questioned 
specifically about the event. In the context of examining the effects of 
overflights on visitors, questions asked about the effects of overflights at a 
specific site, asked right at the site were judged to provide more reliable 
reports of impact than questions asked at the time of exiting the park. 
Second, early research on visitor satisfaction centered upon a single measure 
of visitor satisfaction, but more recent efforts have indicated that a single 
overall measure is inadequate, and now conceptualize visitor satisfaction as 
consisting of multiple satisfactions. In other words, impacts on visitors from 
aircraft are only one of numerous factors that can affect visitor enjovment. 
To understand visitor reactions to aircraft, visitors must be questioned 
specifically about aircraft. 

What these two aspects of visitor satisfaction mean is that impacts of 
overflights can not be easily perceived by broad-brush examination of visitor 
satisfaction long after the experience with overflights occurs. Rather, direct 
questions about the perceived effects of overflights have to be asked 
specifically and close to the time of the experience. Though the visitor survey 
was conducted primarily to permit generalization to the entire park system, 
it also provides useful information for understanding the differences in the 
impacts of overflights at different parks. The Visitor Survey had two parts, an 
initial intercept survey at park exits and a follow-up mail survey. Results of 
the intercept survey are more representative of visitor reaction to overflights 
and less affected by passage of time after the possible exposure to the 
overflights. The best time to ask opinions about overflights is to ask shortly 



132 



6.2 The System-Wide Impacfs of Overflights on Visitors 



after the experience, as was done during the dose-response study conducted 
at specific sites. 

By examining the effects of overflights on visitor enjoyment system-wide, at 
individual parks and at specific sites within parks, the following conclusions 
are drawn: 

System-wide, on an annual basis, about one-fifth of all park visitors (88 
million) report hearing aircraft, and two to three percent (nearly 7 to 1 2 
million visitors) report impacts from these overflights. These numbers 
take on greater significance when problems are concentrated in a 
limited number of parks. So while problems are spread widely enough 
to make a systematic approach desirable, they make simple systemic 
solutions, like the setting of a minimum flight altitude over parks, 
impractical and inappropriate. A systematic approach to problem solving 
must be linked to understanding impacts on a park-by-park, site-by-site 
basis with careful consideration given to the types of visitor experiences 
that the park should be providing. 

Visitor impacts vary significandy park-to-park, and the parks included in 
the Visitor Survey demonstrate this variability. The variation in visitor 
impacts across these parks correlates, though weakly, with NPS 
management rankings of park overflight problems and add weight to 
the conclusion that the 50 to 100 parks identified by management may 
be in need of investigation and remedy. 

Locations that have significant overflight problems can be objectively 
identified and analyzed by using NPS guidelines that include setting 
limits on percentages of visitors impacted and on numbers of visitors 
impacted. 



6.2 The System-Wide Impacts of Overflights 
on Visitors 

The Visitor Survey was designed to provide information system-wide about 
how visitors feel about aircraft overflight related issues. Three survey 
objectives relate to understanding effects on visitor enjoyment. These 
objectives are: 

■ Determine the importance of "natural quiet" to visitors. 

■ Determine the numbers and percentages of park visitors who 
remembered and reported hearing aircraft. 

■ Determine the numbers and percentages of park visitors who 
reported impacts from aircraft overflights. 



133 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



In order to permit generalization of the results to the park system, a 
five-stage sample design was used. This involved selecting: (1) NPS units 
from identified strata, (2) two-month sampling periods, (3) exits and days, 
(4) groups of visitors within those exit-days, and finally (5) a subset of 
visitors to receive a questionnaire in the mail. The result was two sets of 
survey results: those from visitors who were intercepted and interviewed as 
they exited the various parks, and those from visitors who also received the 
mail questionnaire. In the following discussions, the results from the 
intercept or exit survey are used to provide information about the three 
survey objectives listed above . These results are based on visitor responses 
collected during the busiest two months of the season from visitors exiting 
during the busiest 6 hours of the day. 

6.2. 1 Importance of Natural Quiet 

During the intercept survey, visitors were asked how important it was to be 
able "to enjoy the natural quiet and sounds of nature" and "to enjoy the 
natural scenery" as reasons for their visit to the park. Visitors were given five 
choices for responding: not at all important, slightly important, moderately 
important, very important and extremely important. Table 6.1 shows, based 
on the survey responses, what percent and what corresponding annual 
number of park visitors could be expected to answer moderately, very or 
extremely important to these reasons. 

6.2.2 Impacts Produced by Hearing and Seeing Aircraft 

First, visitors leaving the parks were asked if they heard or saw "any 
airplanes, jets, helicopters or any other aircraft during your visit to" the park. 
Table 6.2 presents the results and estimates of the corresponding number of 

1992 visitors who would have heard or seen aircraft. 

Visitors who reported hearing or seeing aircraft were then asked whether 
they were bothered or annoyed by aircraft noise or by seeing aircraft. Visitors 
who heard aircraft were also asked whether the sounds of aircraft interfered 
with three aspects of their visit: enjoyment of the park; appreciation of the 
natural quiet and sounds of nature at the park; appreciation of the historical 
and/or cultural significance of the park. Visitors could respond with one oi 
five answers for each question: not at all, slightly, moderately, very much, 
extremely. Table 6.3 gives the impacts for hearing aircraft, and Table 6.4 
shows the reported annoyance for visitors who saw aircraft. The percents 
shown are percents of the total visitor population, not percents of visitors 
who heard or saw aircraft. 



The mail survey results provide information about visitor perceptions of benefits and about approaches to management presented in Chapters 8 and 9. 



134 



6.2 The System-Wide Impacts of Overflights on Visitors 



TABLE 6.1: IMPORTANCE OF NATURAL QUIET AND NATURAL SCENERY AS 
REASONS FOR PARK VISIT 


Reason for Park Visit 


Estimate 


95% Confidence Interval 


Enjoy Natural Quiet 

Percent of Visitors 
Number of Visitors 
Standard Error c 
(n = 15,150) d 


90.7$ 

397.1 M 

1.23 


88.3% to 93.1% 
386.6 M to 407.6 M 


View Natural Scenery 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n = 15,227) d 


93.2% 

408.0 M 

0.98 


93.1% to 95.1% 
399.7 M to 41 6.3 M 


° Respondents who answered 3, 4, or 5 on the following scale: 1 = not at all 
important, 2 = slightly important, 3 = moderately important, 4 = very 
important, and 5 = extremely important 

Estimate of the 1992 visitor population is 437.8 million visitors. As used here, 
"visitor" means one person exiting the park. Hence, if a person enters and 
leaves a park once each day for three days, that person is counted as three 
"visitors" 
c Standard error is of the percent, not of the number of visitors 

Number of completed interviews 



CONCLUSION 6.1: 

Enjoying the natural quiet is 
about as important as viewing 
natural scenery as a reason for 
visiting national parks. In both 
cases over 90 percent of the 
visitors report moderate to 
extreme importance for both. 



TABLE 6.2: NUMBERS OF VISITORS WHO REPORTED 


HEARING O 


R SEEING AIRCRAFT 






Estimate 


95% Confidence Interval 


Heard aircraft 






Percent of Visitorsa 


20.1% 


10.1% to 30.1% 


Number of Visitors 


88.0 M 


44.2 M to 131.8 


Standard Error 


5.10 


M 


(n = 15,190) 






Saw aircraft 






Percent of Visitors 


1 8.8% 


10.8% to 26.8% 


Number of Visitors 


82.3 M 


47.3 M to 116.3 


Standard Error 


4.10 


M 


(n = 15,081) 






*See notes to Table 6.1 



CONCLUSION 6.2: 

About one fifth of all visitors to 
the National Parks (about 80 
million visitors a year) 
remember seeing or hearing 
aircraft during their visit to the 
park. 



135 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



TABLE 6.3: IMPACTS THAT RESULTED FROM HEARING AIRCRAFT 


Type of Impact 


Estimate 


95% Confidence Interval 


Interfered with Visitor 
Enjoyment 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n = 15,174) 


1 .9% 
8.3 M 
0.65 


0.6% to 3.2% 
2.6 M to 14.0 M 


Annoyed by Hearing Aircraft 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n = 15,174) 


1 .6% 
7.0 M 
0.77 


0.1% to 3.1% 
0.4 M to 13.6M 


Interfered with Appreciation of 
Natural Quiet 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n = 15,049) 


2.8% 

12.3M 

0.99 


0.9% to 4.7% 
3.9 M to 20.6 M 


° See notes to Table 6.1 



CONCLUSION 6.3: 

About 2 to 3 percent of all 

visitors, or roughly from 7 to 13 

million visitors annually, can be 

expected to report impact from 

hearing or seeing aircraft 

overflights. 



TABLE 6.4: ANNOYANCE THAT RESULTED FROM SEEING AIRCRAFT 


Type of Impact 


Estimate 


95% Confidence Interval 


Annoyed by Seeing Aircraft 

Percent of Visitors 
Number of Visitors 
Standard Error 
(n = 15,072) 


3% 

13.1 M 

0.86 


1 .3% to 4.7% 
5.7 M to 20.6 M 


° See notes to Table 6.1 



6.2.3 Impacts Among Different User Groups Produced by Hearing 
Aircraft 

Impacts of overflights on different user groups were also examined. Three 
visitor groups were identified: frontcountry, backcountry, and overnight 
backcountry permit holders. Visitors who completed the exit survey could be 
categorized based on their primary recreational activity. Those who indicated 
their primary activity was backpacking or hiking were classified as 
"backcountry" users, while all other surveyed visitors were classified as 
"frontcountry". The third group, the backcountry permit group, is a sample 
of permit holders from those NPS units that require a permit to stay 
overnight in the backcountry. These permit holders were surveyed by mail. 

Figure 6. 1 shows the percentages of visitors in each of the three groups who 
remembered and reported hearing aircraft, who were annoyed, who 



136 



6.3 Impacts at Specific Parks and at Specific Sites 



indicated aircraft sound interfered with their enjoyment, and who indicated 
aircraft sound interfered with their appreciation of natural quiet and sounds 
of nature. Frontcountry visitors are less likely to report hearing aircraft, and 
to be less impacted by aircraft sounds than backcountry visitors. Such 
differences could be attributed to a number of factors. First, aircraft may be 
less likely to fly at lower altitudes near more populated frontcountry areas, 
possibly avoiding areas where typical frontcountry activities occur. Second, 
backcountry visitors may spend a much longer period of time in the park, 
thus increasing their opportunities to hear aircraft. Third, backcountry 
visitors typically spend a greater portion of their visit away from crowds, 
traffic, noise, etc., in locations where aircraft sounds may be more intrusive. 
Fourth, previous research has shown that backcountry and frontcountry 
visitors generally have different expectations and are seeking different 
experiences in visits to national parks. 



Visitor Impacts Among User Groups 
Exit and Mail Survey Results 





IUO- 
90- 














6 


80' 
70- 
60- 
50- 
40- 
30- 






S 








o 












c 

£ 












.'"..■' 


■ 




20- 








f'ij 










• 




10- 






__M 


':;■:;'; 


__FSSS 






^ 










Head Air 


:roft 


Anno) 


ed 


Interferec 
Enjoyme 


)w/ 
it 


Inte 
Nat 


ferec 
jral C 


w/ 
Duiet 





^^M Exit Survey Frontcountry Activities (n=6,976) 
KSSSJ Exit Survey Backcountry Activities (n= 1 ,928) 
txmml Backcountry Permit Holders (n = 91 1) (Mail Survey) 

Note: Data are from 23 of the 39 Visitor Survey parks where backcountry permits are required for an 
overnight stay. 



Figure 6. 1 : Impacts of Hearing Aircraft Among Different Visitors Groups 



6.3 Impacts at Specific Parks and at Specific Sites 

The previous section presented the broad, system-wide picture of the 
impacts on visitors produced by aircraft overflights. However, both the 
Visitor Survey and the Dose-Response Study provide more information 
about visitor reactions to overflights, the distribution of overflight impacts on 
visitors, the relation of sound level to visitor reaction, and factors affecting 
visitor reactions. This section presents this additional information by 
examining the study results for specific parks and for specific sites within 
parks. 



CONCLUSION 6.4: 

A higher percentage of 
backcountry than frontcountry 
visitors report hearing aircraft 
and are more likely to 
experience impact from these 
aircraft. Though the reasons for 
these differences have not been 
identified, it is clear that hiking 
and backpacking do not 
remove visitors from the 
impacts of overflights. 



137 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



6.3.1 Impacts at Specific Parks 



CONCLUSION 6.5: 

Park visitor reports of exposure 

to aircraft (hearing aircraft) 

and of impacts from the 

exposure vary widely from park 

to park. 



CONCLUSION 6.6: 

The nature and severity of 

impacts at specific sites within 

parks may not be captured by 

the judgments gathered in the 

exit Visitor Survey. 



Percentages of Visitors Impacted 

The Visitor Survey was conducted at a carefully designed and selected sample 
of units of the National Park System. This sample was drawn to permit 
generalization of results to the entire non-Alaskan system of parks. 
However, examination of the data from these individual parks indicates that 
a wide variation in overflight produced impacts exist. Table 6.5 lists the 
parks where visitors were surveyed. It gives also the numbers of visitors who 
were surveyed as they exited the park, and the percent of visitors, weighted 
to reflect the total number of visits during the two month survey period, who 
expressed annoyance, stated that the sound of aircraft interfered with their 
enjoyment of the park or with their appreciation of the natural quiet and 
sounds of nature. 

Figure 6.2 presents graphically for each of the Visitor Survey parks two of the 
quantities listed in Table 6.5: percent of visitors who reported hearing 
aircraft and the percent of visitors who were annoyed. The numbers next to 
the points in the figure indicate the specific park as listed in Table 6.5. As 
shown, parks with higher percentages of visitors reporting hearing aircraft 
also tend to have larger percentages of visitors annoyed by the aircraft. 

Low percentages of visitors impacted in Table 6.5 and Figure 6.2 do not 
necessarily imply no overflight noise problems exist. First, the 
Dose-Response Study, discussed in more detail below, shows that significant 
impacts to visitors can occur at specific sites. Figure 6.3 shows the same 
variables, percent who heard aircraft and percent who were annoyed, for five 
specific sites. Haleakala, Hermit Basin (in the Grand Canyon), and Wahaula 
(Hawaii Volcanoes) all showed more than 20 percent of the visitors to these 
specific sites were annoyed. In Figure 6.2, Haleakala, number 20, Grand 
Canyon, number 17, and Hawaii Volcanoes, number 2 1, all show less than 
10 percent of visitors reporting annoyance with the sound of aircraft 
overflights. If parks such as these that show 5 to 10 percent of the visitors 
are impacted can also have sites in the park where more significant numbers 
are affected, it is likely that the parks of Figure 6.2 that have more than 10 
percent of visitors annoyed also have specific sites where significant 
percentages of visitors are impacted. 



138 



6.3 Impacts at Specific Parks and at Specific Sites 



Table 6.5: Reported Exposure and Impact from Hearing Aircraft at Visitor Survey Parks 


National Park Unit Surveyed 


Number of 

Visitors 
Interviewed 


Percent" of Visitors Reporting 


Hearing 
Aircraft 


Annoyance 


Interference with 


Enjoyment 


Natural Quiet b 


1 


Assateague Island National Seashore 


516 


29 


1 


<1 


3 


2 


Bandelier National Monument 


424 


34 


3 


1 


3 


3 


Buffolo National River 


171 


40 


4 


4 


5 


4 


Canaveral National Seashore 


252 


32 


<1 


2 


4 


5 


Cape Cod National Seashore 


290 


44 


2 


4 


4 


6 


Cape Hatteras National Seashore 


280 


37 


<1 


1 


2 


7 


Casa Grande National Monument 


490 


5 


1 


1 


1 


8 


Cumberland Island National Seashore 


703 


82 


19 


15 


26 


9 


Delaware Water Gap 


277 


22 


1 


1 


2 


10 


Dinosaur National Monument 


598 


8 


1 


1 


2 


11 


Everglades National Park 


268 


49 


17 


17 


21 


12 


Fort Sumter National Monument 


474 


17 


1 


<1 


2 


13 


Fredericksburg & Spotsylvania 


230 


36 


11 


6 


12 


14 


Gettysburg National Military Park 


356 


16 


1 


1 


2 


15 


Glacier National Park 


404 


29 


2 


3 


5 


16 


Glen Canyon National Recreation Area 


285 


52 


4 


4 


8 


17 


Grand Canyon National Park 


536 


34 


5 


5 


10 


18 


Great Smoky Mountains National Park 


266 


12 


1 


1 


3 


19 


Gulf Islands National Seashore 


356 


64 


3 


5 


8 


20 


Haleakala National Park 


533 


47 


6 


6 


12 


21 


Hawaii Volcanoes National Park 


550 


48 


7 


7 


12 


22 


Hot Springs National Park 


623 


13 


1 


1 


1 


23 


Kings Canyon & Sequoia National Park 


304 


13 


3 


3 


5 


24 


Lake Mead National Recreation Area 


199 


32 


1 


2 


3 


25 


Lake Meredith National Recreation Area 


188 


10 


<1 


1 


1 


26 


Lassen Volcanic National Park 


384 


19 


4 


2 


5 


27 


Mount Ranier National Park 


390 


23 


5 


4 


6 


28 


Mount Rushmore National Monument 


530 


61 


9 


10 


17 


29 


North Cascades National Park 


437 


17 


2 


3 


5 


30 


Olympic National Park 


203 


33 


8 


5 


12 


31 


Perry's Victory 


500 


29 


1 


3 


4 


32 


Rocky Mountain National Park 


501 


11 


1 


1 


2 


33 


Saguaro National Monument 


270 


21 


3 


5 


7 


34 


Shenandoah National Park 


458 


13 


4 


4 


5 


35 


Sleeping Bear Dunes National Lakeshore 


372 


16 


1 


2 


3 


36 


Walnut Canyon National Monument 


542 


11 


1 


2 


4 


37 


Wilson's Creek National Battlefield 


453 


19 


1 


2 


3 


38 


Yellowstone National Park 


394 


18 


1 


1 


1 


39 


Yosemite National Park 


337 


55 


15 


14 


19 


a Percents are based on weightings using actual numbers of visitors to each park during the survey periods. 

b Respondents who answered 3, 4, or 5 on the following scale: 1 = not at all, 2 = slightly, 3 = moderately, 4 = very much 

and 5 = extremely 



139 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



Percent Annoyed vs Percent Who Heard 

Visitors Survey Parks 



20- 



15- 



10- 



5- 



■: 
- : ; : ;..■...: ; :. 

- ■■ ■ ••■;••»•• 

• ■ ■— ■■■••■ 

- *'r*' — "I ■ : : 1 : L 



10 20 30 40 50 60 70 80 90 100 
Percenf Who Heard AC 



Figure 6.2: Percent of Visitors Hearing Aircraft and Annoyed by Aircraft 
at Visitor Survey Parks 



Percent Annoyed vs Percent Who Heard 

Five Specific Dose-Response Sites 



50 



40- 



30- 



20- 



10- 



■Haleokala 
: (n = 213)' 



Pt. Imperial 
(1=123)' 



t Basin 
:(n = 3b)' 



Wahoula 
(n = 180) 



Lipan Pi. 
(n = 192)' 



10 20 



30 40 50 60 70 80 90 100 
Percent Who Heard 



Figure 6.3: Percent of Visitors Hearing Aircraft and Annoyed by Aircraft 
at Five Specific Sites 



Numbers of Visitors Impacted 

The impacts of overflights at the specific parks may also be examined by 
estimating the numbers of visitors annoyed during the two month sample 
periods. Figure 6.4 is like Figure 6.2, except estimated numbers of visitors 
are used rather than percents of visitors. Note that Grand Canyon, 17, 
Haleakala, 20, and Hawaii Volcanoes, 21, all are estimated to have more than 
10,000 visitors impacted during the two month survey period. Table 6.6 lists 
the parks of Figure 6.4 having more than 10,000 visitors impacted. 



140 



6.3 Impacts at Specific Parks and at Specific Sites 



Number Annoyed vs Percent Who Heard 

(Number During 2 Month Survey) 




80,000" 

01 
X 

I 60,000- 
< 

o 

S 40,000- 
~o 
m 

-Q 

1 20,000- 

2 


: ■ : 






















.■ 

■ 
........ 

■ 


■ 


™ 






% - - i ■ ■ j 












Number of Visitors Who Heard AC 





Figure 6.4 Numbers of Visitors Hearing Aircraft and Annoyed by Aircraft 
at Visitor Survey Parks 



TABLE 6.6: VISITOR SURVEY PARKS WITH MORE THAN 10,000 VISITORS 
IMPACTED BY OVERFLIGHTS DURING SURVEY 


National Park Unit 


5 


Cape Cod National Seashore 


11 


Everglades National Park 


15 


Glacier National Park 


16 


Glen Canyon National Recreation Area 


17 


Grand Canyon National Park 


18 


Great Smoky Mountains National Park 


19 


Gulf Islands National Seashore 


20 


Haleakala National Park 


21 


Hawaii Volcanoes National Park 


24 


Lake Mead National Recreation Area 


27 


Mount Rainier National Park 


28 


Mount Rushmore National Monument 


29 


North Cascades National Park 


35 


Sleeping Bear Dunes National Lakeshore 


38 


Yellowstone National Park 


39 


Yosemite National Park 



141 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



Comparison of Park Specific Impacts with Management Ratings 

Three different rankings of parks with potential overflight problems were 
developed. First, the National Park Service developed a ranking from 1 , most 
severe, to 9, the least severe for parks within each NPS region. Second, NPS 
developed a national ranking from 1 , greatest potential for aircraft overflight 
exposure, to 3, the least potential. Third, a ranking of "exposure" was 
developed based on limited information about flight routes and air traffic 
information (Tabachnick et al. 1992). These three rankings were examined 
for correlation with visitor reports of hearing aircraft, and with visitor 
reports of impact (McDonald et al. 1994). Modest correlations were found 
for the NPS management rankings and hearing aircraft, and weak 
correlations with impact (annoyance, interference with enjoyment or with 
appreciation of natural quiet). The exposure metric, developed from 
incomplete information about routing of flights and operations numbers, 
correlated to little or no extent with visitor responses. 

Figures 6.5, 6.6 and 6.7 show the relationship of the NPS national ranking 
and the parks included in Pubic Law 1 00-9 1 with hearing aircraft and 
annoyance for the parks of the Visitor Survey. These figures show the 
tendency for the higher ranked parks to be parks were greater percentages of 
visitors report hearing aircraft and where greater percentages or numbers of 
visitors are impacted by hearing aircraft. Reasons for differences between 
management rankings and visitor reactions can be many: management knows 
the purpose and mission of the parks; visitors are at parks generally a few 
days at most; visitors have limited experience with the opportunities offered 
by the park. Nevertheless, very few of the parks with the higher visitor 
impacts are excluded from the higher management rankings. 



O) 



Percent Heard vs Management Rank 

For Visitors Survey Parks 



80 



70-4 

60' 

50 | 

40- 

30 1 

20 

10- 



■Z : 

G> 

; .- : ° 

I ; s 8 



IPL100-91 ▼MngtRankl •MngtRank2 OMngt Rank 3 



Figure 6.5: Comparison of NPS Management Rankings with 
Percent of Visitors Hearing Aircraft 



142 



6.3 Impacts of Specific Parks and at Specific Sites 



Percent Annoyed vs Management Rank 

For Visitors Survey Parks 



20 



151 



10- 



I 

i 



S 



IPL100-91 ▼ MngtRankl •MngtRank2 OMngt Rank 3 



Figure 6.6 Comparison of NPS Management Rankings with 
Percent of Visitors Annoyed 



Number Annoyed vs Management Rank 

For Visitors Survey Parks 



80,000- 



"8 







60,000 


c 

< 









s 


40,000 







c 







20,000 



o 



IPL100-91 ▼MngtRankl »MngtRank2 OMngt Rank 3 



Figure 6. 7: Comparison of NPS Management Rankings with 
Number of Visitors Annoyed 



6.3.2 Impacts at Specific Sites 

The preceding sections of this chapter presented visitor perceptions of 
overflight impacts for the park system as a whole, and showed the variation 
in visitor perceptions from park to park. Since the Visitor Survey could not 
identify what sound levels the visitors experienced, where they went in the 
parks, or how long they stayed in different areas of the park, there is no 
means for inferring this information, and no way to answer questions that 
would help quantify the relationship between visitor reports of impact and 
aircraft sound level. Since the Visitor Survey could not provide any 
information about sound levels experienced by visitors, the Dose-Response 
Study (described in Anderson et al. 1993) was designed and conducted to 
answer the following three questions. 



CONCLUSION 6.7: 

NPS management rankings 
provide a reasonable approach 
to identifying parks with 
potential overflight problems, 
and the management 
perspective is likely to identify 
the parks with the most severe 
visitor impacts. 



143 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



2. 



Does impact as reported by visitors depend upon sound levels 
produced by aircraft overflights? 

If so, what is the relationship between reported impact and 
aircraft sound levels? 



3. What factors other than aircraft sound affect visitor impacts? 

A dose-response relationship may be thought of as a curve on a graph that 
tells what percent of visitors report impact (their response) versus the "dose" 
of aircraft overflight sound. Dose-response relationships have long been used 
to help understand reactions to noise in communities around airports but, 
prior to this dose-response study, there were no data relating how visitors to 
national parks react to the sound of aircraft overflights. 

Dose-response relationships were developed by measuring sound levels in an 
area of a park while simultaneously interviewing visitors who had passed 
through or visited the area. Preparation fordata collection and analysis was 
lengthy, and was highly influenced by the knowledge that, although 
dose-response studies are common in urban airport environments, this exact 
type of study in a park environment had never before been attempted. 
Hence, decisions were made to maximize the likelihood that useful data 
would be acquired. Such an approach meant that variables needed to be 
limited, measurement techniques had to be as simple as possible, and that 
study areas had to be carefully chosen. Table 6.7 lists the specific areas 
studied, the park, the type of area, the dates of data collection, number of 
visitors interviewed and the approximate numbers of aircraft heard per hour. 



TABLE 6.7: DOSE-RESPONSE DATA COLLECTION STUDY AREAS 






National 
Park 


Study 
Area 


Type of Area 


Dates of 

Data 
Collection 


No. of 

Visitors 

Interviewee 


Aircraft 
per Hour 
(approx.) 


Grand 
Canyon 


Havasu 
Creek 


Backcountry, 
stopping point 


27, 28, 29, 
30 Aug. 


30 


9 


Grand 
Canyon 


Point 
Imperial 


Frontcountry, 
overlook 


5, 6 Sep. 


124 


22 


Grand 
Canyon 


Hermit 
Basin 


Backcountry, trail 
segment 


25 Aug. 1, 
2, 3 Sep. 


32 


31 


Grand 
Canyon 


Lipan 
Point 


Frontcountry, 
overlook 


24,26,31 
Aug. 


193 


24 


Haleakala 


Sliding 
Sands Trail 


Frontcountry, short 
hike 


2, 3, 4, 5 
Oct. 


213 


8 to 10 


Hawaii 
Volcanoes 


Wahaula 
Temple 


Frontcountry, short 
hike 


8, 9, 10, 11 
Oct. 


180 


9 to 10 



144 



6.3 Impacts at Specific Parks and at Specific Sites 



The Dose-Response Curves 

Figures 6.8 and 6.9 present dose-response curves that were developed from 

2 
the data for each of the study areas . In each, the horizontal axis gives the 

dose, while the vertical axis gives the response, and the curves show the 

relationship between the two. The two figures are for two doses and one 

response. The doses are percent of time aircraft are audible, and hourly 

equivalent level, Leq,ihr for audible aircraft . The first, percent of time 

audible, was determined by logging the start and end times of all audible 

aircraft overflights. These logs were later correlated with the period of time 

each interviewed visitor was on site to determine the amount of time each 

visitor could have heard aircraft. The Leq,ihr was determined by continuously 

measuring sound levels, then computing for 1 hour periods for each visitor, 

the equivalent level of the sound levels that occurred when aircraft were 

audible (corrected for non-aircraft sound levels). The response is percent of 

visitors who said they were annoyed by aircraft noise while at the site . The 

solid portion of the curve shows where the data lie, the dashed portions are 

extrapolations based on analysis. 



Moderate to Extreme Annoyance 
due to Aircraft Noise in a Park Environment 



100r 




4 6 8 10 20 40 

Percentage of Time Aircraft are Audible 



60 80 100 



Figure 6.8: Dose-Response Curve for Visitor Annoyance vs Percent of 
Time Aircraft are Heard 



Because of the limited number of interviews at Havasu Creek and because aircraft sound levels were so close in level to the non-aircraft background levels 
that doses could not be computed, the Havasu Creek data could not be used in developing the dose-response curves. 

Percent of time aircraft are audible, while simple to measure, is extremely difficult to predict. On the other hand, measurement of Z e q,lhr of audible 
aircraft is somewhat difficult, but reasonably easy to predict with current available computer models. Hence, dose-response curves for both metrics have 
been developed to provide the tools necessary Jor measurement, analysis and mitigation of overflight noise problems in parks, see section 6.4. I e q,lhr «s the 
computed dose that occurred during the hour that the visitor was at the site. Use of this dose Jor assessing a site assumes that the relationship between 
itq.lhr and the actual dose received by the visitor at the site is similar to the relationship at the dose-response sites were the data were collected. 

The response of annoyance rather than interference with enjoyment was chosen Jor two reasons. Primarily, annoyance is the metric of response that has 
been used Jor almost two decades to assess the impact of intruding sounds, and particularly aircraft sounds on humans. The use of annoyance thus 
continues a well-established approach. Second, visitor impact in terms of annoyance and m terms of intejerence with enjoyment have proven to be 
virtually identical, see Jor example Table 6. 5. Curves were also developed Jor the dose of intejerence with the natural quiet and sounds of nature. 



145 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



Moderate to Extreme Annoyance 
due to Aircraft Noise in a Park Environment 



100 




pan Point 



10 20 30 40 50 60 70 80 

Hourly Equivelent Sound Level (L e q. I hr) of Audible Aircraft (dB) 



Figure 6.9: Dose-Response Curve for Visitor Annoyance vs 
Hourly Equivalent Sound Level 



CONCLUSION 6.8: 

Visitors report negative 

reactions to the sound of 

aircraft at specific sites, and 

these negative reports increase 

as exposure fo aircraft sounds 

increase. 



CONCLUSION 6.9: 

Dose-response curves quantify 

the relationships between 

overflight sound levels and 

visitor impacts. Not all 

non-sound level factors that 

influence visitor impacts can be 

identified, but sufficient 

information is available that 

careful use of the 

dose-response curves can 

identify sites likely to produce 

significant impacts on visitors. 



The dose-response curves, to the extent that they are applicable to a given 
site, can be used to predict visitor responses (impacts) by measuring (or 
predicting) dose. For example, if monitoring at a site similar to Sliding Sands 
shows aircraft audible about 30 percent of the time, then Figure 6.8 predicts 
that about 32 percent of the visitors will be annoyed. Alternatively, if Leq ( ihr 
of 40 dB from audible aircraft were measured or predicted for the site, 
Figure 6.9 shows that about 37 percent of the visitors will be annoyed. Thus 
through measurement and/or prediction, the magnitude of the visitor 
impacts may be determined. Analytical methods can then be used to identify 
possible solutions. Section 6.4 below discusses such a monitoring, analysis 
and mitigation process in more detail. 

These curves demonstrate that sound exposure, though an important 
variable, is not the sole determinant of impact on visitors. Not only do the 
impacts on visitors clearly vary considerably from one site to another, but 
statistical testing of the data has shown that several other specific factors 
affect visitor response. Though the importance of these factors varies 
depending upon which dose and which response are examined, some 
generalizations are possible. First time visitors to a site are less sensitive to 
aircraft sound than are repeat visitors; visitor "groups" of one or two people 
are more sensitive than are larger groups; visitors who thought enjoying the 
natural quiet and sounds of nature was a very or extremely important reason 
for visiting the site were more sensitive to aircraft sound than visitors who 
judged quiet and sounds of nature as less important. These three factors can 
have a significant effect on visitor response. Repeat visitors, or groups of 1 or 
2, or visitors who rate quiet as very important respond as it the sound were 
about two to three times as long or about 20 dB louder when compared with 
first time visitors, larger groups, or visitors who do not so highly value quiet. 



146 



6.4 Identification, Analysis and Mitigation of Impacts 



The dose-response data also suggest other factors that may be important in 
affecting how visitors respond, but lack of data prevented developing 
statistically verifiable results. The type of site is clearly important, since the 
curves vary from site to site; what is unknown is what characteristics of the 
site are important. For example, the non-aircraft sound levels at a site seem 
to affect response, the higher the non-aircraft sound levels, the less the 
visitor response. Sites that are more easily accessible seem to be visited by a 
population of visitors that are less sensitive to aircraft sounds; conversely, the 
less accessible sites, where visitors must walk some distance, may attract 
more sensitive groups of visitors. Virtually all overflights were light tour 
propeller and helicopter aircraft, flying at moderate altitudes (less than 1 000 
to 2000 feet, but generally higher than several hundred feet); visitor 
responses to aircraft at very high or very low altitudes, or to other types of 
aircraft, especially jets, are unknown. More data are needed if these factors 
are to be reliably identified and quantified. 



6.4 Identification, Analysis and Mitigation of 
Impacts 

When used in conjunction with NPS management judgement, the 
dose-response results provide a means for quantitatively identifying and rank 
ordering sites within parks that potentially produce significant impacts on 
visitors. This section presents in oudine form a method that can be used for 
the process of identification, analysis and mitigation of the types of visitor 
impacts discussed in previous sections of this chapter. 

6.4. 1 Identification 

NPS management judgement and priority setting provide the primary basis 
for initial identification of units of the National Park System likely to have 
areas where overflights are producing significant visitor impacts. Not only 
does the management perspective consider the purposes, resources and 
intended recreational opportunities of the parks but, as discussed above in 
section 6.3.1, the management perspective as reflected in the NPS 
management rankings of parks demonstrates some correlation with the 
impacts reported by visitors for the Visitor Survey_parks. Hence, the first 
step in identification of potential problem areas is to use the management 
rankings of highest concern parks (50 to 100 parks), identify the top priority 
parks for problem solving, and then identify the most impacted sites within 
them. 



147 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



Identifying candidate sites within the priority parks will require an orderly 
identification of site characteristics. Important criteria for consideration will 
include: 

1 . Frequency of Overflights — How many overflights per hour occur 
regularly during periods of visitation? 

2. Visitation Rates — How many visitors per hour or per day pass 
through the candidate site? 

3. Recreational Opportunity — What are the important dimensions 
of the intended opportunity: unobstructed views, solitude, 
remote location, transportation access, etc.? 

Once candidate sites are identified, the dose-response curves based on the 
percent of time aircraft are audible can be used by park personnel to develop 
a quantitative evaluation of the site. Percent of time audible data can be easily 
collected and compared with an appropriate dose-response curve for the 
site. Ideally, the curve used would be the one derived from the 
dose-response site most similar to the site in question. However, to simplify 
selection of the appropriate curve, Figures 6. 10 and 6. 1 1 have been 
developed. Each provides a curve for two generic types of sites: short-hike 
(or backcountry) and overlooks (or front country) sites. The "Short-hike 
Sites" curves are derived from the results obtained at Hermit Basin, Sliding 
Sands Trail and Wahaula Temple, weighted for sample size and statistical 
reliability. The "Overlooks curves" are similarly derived from the Point 
Imperial and Lipan Point data. 

Figure 6. 10 is to be used for sites where preservation of natural quiet is not 
one of the primary concerns, while Figure 6. 1 1 provides curves to be used 
for sites where preservation of natural quiet is very important. 

Park personnel would collect time audible data, using a carefully designed 
sampling procedure, and compare the results to the appropriate curve to 
estimate the degree of impact. The NPS would set criteria for acceptable 
degrees of impact, identifying both maximum acceptable percentages and 
maximum acceptable numbers of visitors impacted for each type of site or 
activity. If these maximums are exceeded, the NPS would initiate a process 
of analysis and interaction with aircraft operators and other agencies (eg., the 
FAA, DOD, etc.) to eliminate or reduce the impacts. 

The criteria for maximum acceptable impact would be developed by the NPS 
in terms of both percent of visitors to a site and numbers of visitors to a site. 
In terms of percent of visitors, a maximum acceptable value might be 
between 20 and 30 percent. Then, for example, where park measurements 
show a dose that results in more than 25 percent of visitors impacted, 
analysis and mitigation efforts would commence. Maximum acceptable 
numbers of visitors impacted would also be identified. 



148 



6.4 Identification, Analysis and Mitigation of Impacts 



Moderate to Extreme Annoyance 
lue to Aircraft Noise in a Park Environment 



100 
90 
80 
70 
60 
50 
40 
30 
20 
10 




- :■• 
















\ :• 




\\\\\ j \ 


..;..;..;..;..;..;. 


■ \- 




: Shorl-hike Sitesi,, 


^J^*"^ ■ 





















4 6 8 10 20 40 

Percentage of Time Aircraft are Audible 



60 80 100 



Figure 6.10: Dose-Response Curves for Estimating Impacts at Sites 
Preserving Visitor Enjoyment 



Moderate to Extreme Interference with 

Natural Quiet due to Aircraft Noise 

in a Park Environment 



100 
90 
80 



o x 

•t: <u 


70 






S £ 


60 






o <u 
0) 5 


50 


0)Q 




o Z. 


40 


c P 




<u a 

12 


30 
?0 


^ 








s 


10 




4 6 8 10 20 40 

Percentage of Time Aircraft are Audible 



60 80 100 



Figure 6.11: Dose-Response Curves for Estimating Impacts at 
Sites Preserving Natural Quiet 



6.4.2 Analysis and Mitigation 

A flexible approach to analysis and mitigation will be developed and pursued. 
In some cases, for example, discussions with aircraft operators may identify 
simple changes (for example re-routings of air tours) that can be tested, 
found to provide acceptable reductions of impact, and implemented. In 
other cases, detailed analyses of many alternatives may be necessary. In such 
cases, the simple time audible metric can no longer be used. This metric, as 
mentioned, is extremely difficult to predict, and the alternative 
dose-response curves using hourly equivalent sound level, Leq,ihr, of audible 
aircraft will be employed. 



149 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



Detailed analyses of aircraft produced sound levels have long been conducted 
for airports and military air facilities. These efforts have resulted in computer 
models that can predict, generally within acceptable tolerances, how sound 
levels on the ground will be altered by changes in airspace use. These models 
are being adapted or expanded to provide predictive capabilities for aircraft 
overflights of parks (Reddingius 1994). Using these computer models and 
information about airspace use including aircraft types, number of flights per 
day, location of flight corridors, altitudes of flights and terrain features, 
Leq,lhr, can be computed for current operations and predicted for future or 
proposed operations, and Figures 6. 1 2 or 6. 1 3 can be used to estimate 
resulting visitor impacts. 



Moderate to Extreme Annoyance 
due to Aircraft Noise in a Park Environment 



100 




10 20 30 40 50 60 70 80 

Hourly Equivalent Sound Level (l-eq. 1 hr) of Audible aircraft (dB) 



Figure 6. 12: Dose-Response Curves for Analysis of Airspace at Sites 
Preserving Visitor Enjoyment 



Moderate to Extreme Interference 

with Natural Quiet due to Aircraft Noise 

in a Park Environment 



oO 



&2 



100 




10 20 30 40 50 60 70 80 

Hourly Equivalent Sound Level (L e n ; nr ) of Audible aircraft (dB) 



Figure 6. 12: Dose-Response Curves for Analysis of Airspace at Sites 
Preserving Visitor Enjoyment 



150 



6.4 Identification, Analysis and Mitigation of Impacts 



As discussed above, ideally the curve used would be the one derived from the 
dose-response site most similar to the site in question. However, since 
current understanding of all of the factors that distinguish one dose-response 
site from another is limited, the curves of Figures 6. 1 2 and 6.13 are 
conservatively (in a protective sense) derived from the results for the study 
area that consistendy had the highest level of visitor response for a given level 
of aircraft sound, Sliding Sands at Haleakala National Park. The curves for 
Sliding Sands are higher than those for Wahaula Temple, Point Imperial, and 
Lipan Point. The curves for Sliding Sands are slightly lower than those for 
Hermit Basin, but the Sliding Sands curves were chosen over those for 
Hermit Basin due to the larger sample size and greater range of Leq,ihr 
measured at Sliding Sands, see Table 6.7 and Figure 6.9. 

Using the computer models, working with aircraft operators and appropriate 
other government agencies, NPS would quantify alternatives and identify 
effective, feasible changes that reduce visitor impacts to acceptable levels. 

6.4.3 Limitations 

There are some limitations to this approach to identification, analysis and 
mitigation, and these limitations derive from the limited data upon which the 
dose-response curves are based. NPS will recognize the following limitations 
in use of these curves. 

1 . The curves are based on visits to specific areas, not visits 
to entire parks. The study's data were collected on visitor 
reactions and sound levels in specific areas, and therefore should 
be applied to visits to specific areas only and not extended to an 
entire park visit. Many sites within a park may be individually 
considered, but there is no simple way to extend the results to 
overall visitor reactions that result at the end of a stay in a park. 

2 . The curves are based on visits of relatively short duration. 

All study areas were located where visitors were in the area for 
periods of 2 hours or less. The results have not been tested for 
visits of much longer deration, such as daylong or overnight stays, 
though sites with longer visit durations of up to four to five hours 
can probably be analyzed accurately. 

3. The curves apply to audible aircraft sounds only. The 

dose-response curves, in terms of Lea, ihr> are for use where 
aircraft are audible. Predictions of aircraft sound levels may not 
accurately account for all aspects of aircraft sound generation and 
propagation, so care must be used in developing estimates of 
Leq,lhr that take audibility into account. For example, moving 
aircraft flight corridors may result in some types of aircraft, or 
some portions of aircraft flight, becoming inaudible at a specific 



151 



REPORT TO CONGRESS: Effect of Overflights on Visitor Enjoyment 



site. This reduction in audibility must be incorporated into 
Leq.lhr if Figure 6.12 or 6.13 is to provide accurate estimates of 
impact. 

4. The curves are based on scenic parks. The parks in which 
the data were collected all attract visitors for their scenic, natural 
qualities. At the selected study areas, visitors were hiking or 
sight-seeing outdoors. The background environments at these 
areas were primarily natural, although human noises and parking 
lot noises were present at the overlooks. The results can probably 
be used for other scenic natural parks with similar conditions, and 
for visitors participating in similar activities, but their applicability 
to sites with indoor activities or to stricfiy cultural or historic 
parks, or parks in urban or suburban areas has not been verified. 

5. The curves are based on tour aircraft in level flight. 

Primarily light propeller and helicopter tour aircraft in level flight 
were observed during data collection. The results may be applied 
to similar conditions, but their applicability to jet aircraft, very 
large aircraft, or to areas where aircraft are noticeably climbing or 
descending has not been tested. 



6.5 Summary 

System-Wide 

For the National Park System as a whole, about one-fifth of the visitors (88 
million) report hearing or seeing aircraft, and 2 to 3 percent of all visitors (7 
to 12 million visitors) report having their enjoyment interfered with, being 
annoyed or having their appreciation of natural quiet interfered with by the 
sound of aircraft. The NPS has a problem. It is not systemic with problems 
in every park. The number of parks and visitors impacted is limited. Rather, 
it is the case that serious problems are occurring in a limited number of 
parks scattered across the country in which pockets of visitors are impacted. 
It is a serious problem in search of a measured solution. The NPS considers 
it akin to the proverbial canary in the mine; finding solutions should not be 
delayed while the duration of the canary's song is measured. 

Yet the complexity of park overflight problems does not lend itself to simple 
solutions such as setting minimum altitude restrictions for flights over all 
parks. A systematic approach is needed, but an approach that will focus on 
the most serious problems and have them understood in terms of impacts on 
visitors, individual parks, and specific locations within parks. 



152 



6.5 Summary 



Individual Parks 

Visitor impacts vary widely park to park. Low percentages of visitors 
impacted, however, cannot be taken to mean that there are no locations 
within a park where significant impacts occur. NPS management rankings 
show a modest, but recognizable correlation with visitor impacts. 

The conclusion is that very different numbers of visitors report impacts from 
overflights, park to park, and that park management has been able to provide 
a reasonable rank ordering that shows some correspondence with these 
variations. Hence, out of a total of about 340 park units, there may actually 
be about 50 to 100 parks (6 PL 100-91 units, 49 Management Rank 1 units 
and 45 Management Rank 2 units) with overflight problems in need of 
investigation and remedy. 

Specific Sites 

All system-wide and park specific conclusions about impact on visitor 
enjoyment are based only on visitor responses with no knowledge of visitor 
exposure to aircraft sound. The site specific dose-response data provide both 
visitor response and aircraft sound exposure. These data show that visitors 
who are exposed to the sound of aircraft do report impacts, and that reports 
of impact increase with increasing exposure to aircraft sound. Further, 
reports of impact are dependent upon many factors that may or may not be 
related to the specific site. Such differences in response by sound exposure 
and by location have three major implications. First, lowering sound 
exposure will reduce impacts on visitors, meaning that some reduction of 
sound levels is beneficial even if total elimination of intruding aircraft sound 
cannot be achieved. Second, the NPS can set guidelines for minimizing 
impacts on visitors by selecting maximum acceptable percents and numbers 
of visitors impacted at a specific park site or for a specific recreational 
opportunity. Third, some areas and visitor activities are more important to 
isolate from overflights than others, meaning that moving overflights to less 
sensitive areas of a park may be warranted. 



153 



^%5^ 



7 



AIRCRAFT OVERFLIGHTS AND SAFETY 

Section 1(c) of Public Law 100-91 mandates that the National Park Service 
assess the safety of on-ground visitors relative to aircraft overflights: 

The research at each such [park] unit shall provide information 
and an evaluation regarding each of the following: 

(1) the impacts of aircraft noise on the safety of the park 
system users, including hikers, rock-c/imbers, ond 
boaters. ..." 

The NPS addressed this question through the Park Manager Survey, the 
system-wide Visitor Survey, and by contacting numerous outdoor recreation 
organizations who might have knowledge of the issue. Results are discussed 
in the following sections. 



7. 1 Concerns of Park Management 

Visitor safety is a major concern of NPS managers and park staff. In order to 
obtain the broadest possible perspective about these concerns as they may be 
related to aircraft overflights, the Park Manager Survey (HBRS, Inc., 1993) 
included questions about aircraft and visitor safety. Questionnaires were sent 
to 98 park managers whose units had previously been identified as having 
aircraft overflight concerns. Of the 98 parks, 91 provided detailed responses. 
The responses provided by these managers give insight into the nature and 
extent of the perceived problem in the National Park System. Although 
statistical inference cannot be made to the entire system, the. NPS is 



155 



REPORT TO CONGRESS: Aircraft Overflights and Safety 



confident that this information is representative of the nature and extent of 
agency concerns and certainly reflects those situations where aircraft 
overflights have generated a level of management concern. 

Managers were asked their opinion on how much of a problem aircraft 
overflights posed to visitor and staff safety at their park. Figure 7 . 1 reports 
the results. Of the 9 1 parks responding, 62 percent of the managers either 
said that overflights were not a safety problem, or that they were only a slight 
problem. Another 20 percent indicated overflights were a moderate safety 
problem. The remaining 1 8 percent, however, responded that overflights 
were a serious or very serious safety problem. Table 7. 1 identifies the parks 
where serious and very serious problems are perceived. 

In the same survey, managers were also asked to provide some detail as to 
the nature of their safety concerns. Table 7.2 provides an alphabetical listing 
of the parks from Table 7.1, the nature of management's safety concerns, 
and the type of aircraft typically involved. This table shows a diverse range of 
safety issues. The NPS recommends that these situations be investigated by 
theFAA. 



Manager Assessment of Visitor and Staff Safety 



50 



40-- 



30 ■■ 



20- 



10-- 





35 










— i 1 i 




it 






Ililii 

y'-yyyy- yyyy yyyyyy. 




20 




. 


a... 




10 


i 1 










i 
1 



None Slight Moderate Serious Very Serious 

Extent of Problem 



Figure 7. 1 : Manager Assessment of Visitor and Staff Safety 



156 



7. ? Concerns of Park Management 



Perceptions Managers Have About 
Visitor and Staff Concerns for Safety 



Not at a 



Park Visitor Concerns 
1 Park Staff Concerns 




Slightly Moderately Very 

Degree of Concern 



Extreme 



Figure 7.2: Perceptions Managers Have About Visitor and Staff Concerns for Safety 



TABLE 7.1 PARKS WHERE SAFETY IS PERCEIVED AS A SERIOUS, 
OR VERY SERIOUS PROBLEM 



VERY SERIOUS PROBLEM 



Chaco Culture National Historic Park 



City of Rocks National Reserve 



Fort Vancouver National Historic Site 



Gateway National Recreation Area 



Glen Canyon National Recreation Area 



Sequoia & Kings Canyon National Parks 



Pipe Spring National Monument 



Prince William Forest Park 



Statue of Liberty National Monument 



SERIOUS PROBLEM 



Big Bend National Park 



Bryce Canyon National Park 



Channel Islands National Park 



Fire Island National Seashore 



Gulf Islands National Seashore 



John Day Fossil Beds National Monument 



Perry's Victory & International Peace Memorial 



157 



REPORT TO CONGRESS: Aircraft Overflights and Safety 



fcp- 




TABLE 7.2 VISITOR SAFETY CONCERNS REPORTED TO PARK MANAGEMENT DURING FY 1992 


PARK 


SAFETY CONCERN 


AIRCRAFT 


Chaco Cultural National Historic Park 


Low-flying aircraft 


Propeller 


City of Rocks National Preserve 


Low-flying aircraft 


Jet/Propeller 


Fort Vancouver National Historic Site 


Low-flying aircraft 


Jet/Propeller 


Gateway National Recreation Area 


Visitor Safety & Aircraft Crashes 


Helicopter 


Glen Canyon National Recreation Area 


Risk of Collision 


Helo/Prop 


Sequoia & Kings Canyon National Parks 


Low-flying aircraft 


Jet/Helo 


Pipe Spring National Monument 


Low-flying aircraft 


Jet 


Prince William Forest Park 


Low-flying aircraft 


Helo/Jet 


Statue of Liberty National Monument 


Visitor Safety & damage to monument 


Helicopter 


Great Smokey Mountains National Park 


Low-flying aircraft spooked trail horses 
Collision Risk 


Helicopter 
Helicopter 


Big Bend National Park 


Low flying aircraft spooked trail horses 


Jet 


Bryce Canyon National Park 


Low-flying aircraft 


Helicopter 


Channel Islands National Park 


Low flying aircraft 


Propeller 


Fire Island National Seashore 


Low flying aircraft 


Propeller 


Gulf Islands National Seashore 


Aircraft landing in park 


Helicopter 


John Day Fossil Beds Nat'l Monument 


Low-flying aircraft 


Jet/Prop 


Perry's Victory & International Peace Memorial 


Aircraft flying dangerously close to landmark 


Helo/Prop 



The NPS needs to further evaluate situations where moderate problems are 
perceived to exist. Moderate problem priorities would include Hawaii 
Volcanoes National Park where aircraft are believed to be flying dangerously 
low over visitors and molten lava and where visitors have been struck by 
gravel, wind, and rotor wash and the Great Smoky Mountains National Park 
where helicopters have been reported to have spooked trail horses and the 
superintendent is concerned about a possible mid-air collision. 

The FAA is already looking at the safety situation in Hawaii where from 
1991-1993 there have been 46 sightseeing aircraft and rotorcraft accidents 
resulting in 46 injuries and 37 fatalities. FAA inspectors have accompanied 
park rangers and resource managers to document instances of inappropriate 
and dangerous flying over Hawaii Volcanoes National Park, including flying 
through volcanic fumes and low over molten lava. 

Managers were also asked to indicate the degree to which they perceive 
visitors and park staff are concerned about their own safety as a result of 
aircraft overflights over their park. The results are shown in Figure 7.2. In 
general, the result shows that managers believe visitor and staff concerns to 
be about the same. About 74 percent of the managers felt that staff and 
visitors were not concerned or were only slightly concerned about personal 
safety. Approximately 10 percent felt these two groups were moderately 



158 



7.2 Concerns of Pork Visitors 



concerned; only 6 percent of the managers felt that visitors and staff were 
very or extremely concerned about safety in their park. 

The difference in perception between managers and visitors is, in part, a 

function of the managers' responsibility for visitor safety, but it also may 

reflect the number of crashes that have occurred in NPS areas. Through the 

survey, managers provided a listing of aircraft incidents (crashes) that 

occurred in their parks during the past 5 years. A summary of the 

information provided is presented in Figure 7.3. The figure shows the 

number of incidents, in terms of type of activity, reported by the managers. 

This figure shows blocks of varying heights which indicate the total number 

of incidents. Propeller-driven general aviation airplanes, propeller-driven 

sightseeing airplanes, and military jets were the types of aircraft most 

2 
frequendy involved. 



CONCLUSION 7.1: 

Relatively few park managers 
perceive safety concerns to 
park visitors and staff from 
aircraft overflying their parks. 
Attention needs to be given to 
those few parks where serious 
or very serious safety issues are 
perceived. 



7.2 Concerns of Park Visitors 

Similar questions were included in the survey of park visitors that was 
conducted in 1992 (McDonald et ai. 1994) at 39 parks representing the 
National Park System (excluding Alaska). In the mail survey that was sent to 
selected survey participants were questions relating to visitors' perceptions 
on safety from aircraft flying overhead. 

In one series of questions, visitors were asked how hearing or seeing aircraft 
affected their visit to the park. A specific question asked how concerned they 
were about their safety from aircraft flying overhead. The responses are 
shown in Figure 7.4. Visitors indicated their degree of concern by selecting 
one of the five categories shown at the bottom of the graph. The figure 
shows that 99 percent of the respondents were either not at all or only 
slighdy concerned. Just 1 percent of the visitors reported being moderately 
concerned about their safety, and none reported being very or extremely 
concerned. This is a good indicator that any safety problems are occurring in 
relatively few places and very infrequendy at that. The greater degree of 
concern among managers as compared to visitors is also undoubtedly related 
to a long term exposure to overflight incidents and their overall responsibility 
for visitor safety. Short-term visitors simply don't have that exposure or 
responsibility. 



/ . It is the understanding of the NPS that all these incidents were reported to the VAA and investigated by the National Transportation Safety- Board 
(NTSB). 

2. Miscellaneous incidents include those involving ultra-liahi aircraft, a alider. a hot air balloon, and a blimp whose tether line struck the Statue of Liberty. 



159 



REPORT TO CONGRESS: Aircraft Overflights and Safety 



In a counter-question, visitors were also asked if aircraft overflights made 
them feel safer in case they needed rescue. Figure 7.5 shows the responses. 
For this question, 90 percent of the respondents said that aircraft proximity 
did not increase their feeling of safety, or if so only slightly. However, 1 
percent of the visitors did report an increased feeling of safety, to a 
"moderate", "very", or "extreme" degree. 



Reported Aircraft Crashes in 
91 NPS Units During Past Five Years 



25 



20-- 



15-- 



10-- 



5-- 



23 



17 



ii plm m i 



Administrative Sightseeing Military General Filming Air Show 

Aviation 
Aircraft Operator 



Figure 7.3: Reported Aircraft Crashes in 91 NPS Units During the Past Five Years 



100 



Visitor Assessment of Personal Safety 

Concerned About Safety 



£■ 80--; 



60 



40-- 



20 



98 



Not at all 



1 



1 



Slightly Moderately 

Degree of Concern 



Very Much Extremely 



Figure 7.4: Visitor Assessment of Decreased Feelings of Safety 
Due to Aircraft Operations 



160 



100 



80 ■ ■ 



60 ■ ■ 



40 ■• 



20 ■■ 



Visitors Feeling Safer 
Because of Aircraft Proximity 





82 




lilllll 














8 A A 




^y*WW*£J 4 4 7 



Not at all 



Slightly Moderately Very Much Extremely 

Feeling of Increased Safety 



Figure 7.5: Visitor Assessment of Increased Feelings of Safety 
From Aircraft Overflights 



7.3 Outdoor Recreation Community Concerns 



CONCLUSION 7.2: 

Virtually no visitors perceive 
concern for their safety from 
aircraft overflights, an indicator 
suggesting that any safety 
problems are occurring in 
relatively few places and 
infrequently. 



7.3 Outdoor Recreation Community Concerns 

In 1993 the NPS wrote to a broad array of outdoor recreation groups to 
inquire whether they could identify any on-the-ground safety issues related 
to aircraft overflights of the National Park System during the last 10 years. 
Groups contacted included, among others, the following organizations: 

American Alpine Club 

The Wilderness Society 

Colorado Mountain Club 

Sierra Club 

American Mountain Guides Association 

National Outdoor Leadership School 

Colorado Outward Bound 

Backcountry Horseman of America 

A limited number of written and verbal responses were received. Most of the 
comments dealt with the startle effect of aircraft on themselves, clients, or 
friends. No serious or lasting injuries were reported. Several comments dealt 
with the inherent incompatibility of horses and helicopters and offered 
examples of this incompatibility. The writers of the letters also used the 
opportunity to voice concern about wildlife harassment by aircraft and the 
impact of aircraft on visitors' experience in remote areas of parks. 



CONCLUSION 7.3: 

Although some outdoor 
recreation organizations 
indicated a low level of concern 
on safety related to aircraft 
overflights, this level again 
suggests local or infrequent 
problems as well as concerns 
for other types of impacts. 
Ensuring a segregation between 
helicopters and horse traffic in 
some situations may be 
desirable. 



161 



REPORT TO CONGRESS: Aircraft Overflights and Safety 



CONCLUSION 7.4: 

As airspace over public lands 

becomes more congested, the 

potential for conflicts is 

increasing. Although progress 

is being made in resolving 

these airspace issues, the 39 

near-misses in 1992 indicate 

the need for improved 

communication links at an 

operational level between FAA, 

Department of Defense 

agencies, the NPS and other 

land management agencies. 



7.4 Temporary Flight Restriction (TFR) Problems 

Low-level airspace over public lands can sometimes be very busy. This 
airspace can be attractive to air tour operators as well as to general aviation. 
It is at these altitudes that much military tactical training occurs. They are 
the same altitudes where the NPS and other land management agencies 
conduct wildlife surveys, animal capture and control flights, law enforcement 
flights and aerial firefighting. The potential for conflict is significant, 
especially in bad fire years. In 1992, 59 airspace conflicts involving 
Department of the Interior aircraft were reported. Of these, 39 were near 
mid-air collisions — 1 1 with military aircraft and 28 with civilian aircraft. 
Characteristically, conflicts with military aircraft generally occur in the 
Western United States where there is a concentration of military training 
routes and military operations areas. Conflicts with civilian aircraft more 
often occur in the higher density air traffic areas along the Eastern seaboard. 

The FAA, Department of Defense, and Department of the Interior have 
already begun to work on this issue. Apparendy the key to resolving this 
safety problem is dissemination of the Temporary Flight Restriction (TFR) 
information to pilots who are already in the air when the notice is issued. 
TFR's are issued through the FAA (Federal Aviation Regulation 9 1 . 37 A) and 
distributed to pilots using FAA's "Notice to Airmen" (NOT AM) system. 
Great numbers of these NOTAMs are issued every day dealing with a myriad 
of topics which make it difficult for pilots to identify which ones will affect 
their routes. This is especially true of military pilots who may be flying across 
the country. 

Communication is the crux of the issue. Direct coordination, especially with 
the military would help, but it is difficult for the NPS and other land 
management agencies to know with whom they should talk. A simple, 
national level system is needed to rapidly disseminate airspace information to 
all pilots. Progress has been made: 

■ The Bureau of Land Management and the Forest Service are 
developing a "Computer-aided Aviation Hazard Identification 
System" (CAHIS) to assist natural resource agencies in planning air 
operations in areas which have a high volume of military activity. 

■ The Department of the Interior has petitioned the FAA to create a 
separate and distinct transponder code to be used by natural 
resource aircraft for radar identification. This transponder code 
would be available in the near future. 

■ The Department of Defense is exploring communication links for 
scheduling military training routes and special use airspace. 



162 



7.5 Summary 



7.5 Summary 

There is no evidence of any serious or wide spread safety problem for 
on-ground visitors or park employees tied to aircraft overflight. There are 
problems in a limited number of areas that should to be addressed. 
Problems in a number of other areas should be evaluated further. Only a few 
managers and virtually no visitors perceived any safety problem related to 
aircraft overflight. Some elements in the outdoor recreation community 
expressed concern, but the incidents triggering these concerns are probably 
isolated and could be dealt with in the context of a better reporting system. 
Procedures and communications are currendy lacking, and this is a problem 
that the involved agencies can address if they are willing to work together to 
prevent problems. The potential seriousness of the situation should not, 
however, be ignored. On the Pacific Crest Trail in 1988, an Oregon couple 
were thrown from their horses as a result of a low-level flight; the man had a 
fractured skull and his wife broke her back, collarbone, and a rib. 

The NPS and other land management agencies should work with the DOD 
and FAA to develop procedures for use in dealing with the airspace/park use 
issues that occur in complex airspace (i.e special use airspace, military 
operations areas and military training routes) especially during fire fighting 
or other major incidents. Important steps have been taken, but 
communications at an operational level should be significandy improved. 



163 



tf0*f?fe 



8 



VALUES ASSOCIATED WITH AIRCRAFT 
OVERFLIGHTS 

Section 1 of Public Law 100-91 mandates that the National Park Service 
assess the values associated with aircraft overflights of parks: 

The research at each such [park] unit shall provide information 
and an evaluation regarding each of the following. . . 

"(4) the values associated with aircraft flights over such 
units of the National Park System in terms of visitor 
enjoyment, the protection of persons or property, search 
and rescue operations and fire fighting. '"' 

The NPS interpreted this to mean that it should assess the values associated 
with administrative and air-tour overflights, and that military, commercial, 
and general aviation flight activity should not be included within the scope of 
investigation. Consequendy, this chapter reports on four topics: the values 
accruing to parks and park visitors from the NPS administrative overflights, 
the values associated with air tour flights of parks, the value of the air tour 
industry to local economies, and the values associated with aerial movie 
filming. 



8. 1 Values Associated with Administrative Use 
of Aircraft 

Many units of the National Park System use aircraft to assist with 
management activities. Whether chartered, leased, or owned by the NPS, 



165 



REPORT TO CONGRESS: Values Associated with Aircraft Overflights 



these aircraft must overfly the park by the very nature of their duties. Across 
the National Park System, in a twelve month period between 1992 and 
1993, the NPS logged 19,133 hours of aircraft use. The Park Manager 
Survey (HBRS, Inc., 1993) to the subset of 98 parks indicating some type of 
aircraft overflight problem provides more insight about the NPS use of 
aircraft. The responses from the 9 1 parks that returned completed 
questionnaires are examined in this section. 

In the survey, managers were first asked whether their park ever used aircraft 
in an administrative capacity; sixty-five percent of the parks surveyed 
reported using aircraft, almost twice as many as did not. Querying further, 
the questionnaire asked those managers answering in the affirmative what 
type of aircraft were used (helicopter or fixed- wing). Virtually all the parks 
surveyed used helicopters, and approximately 3/4 of the parks surveyed use 
fixed-wing aircraft. The majority of parks use both types of aircraft. (For the 
National Park System as a whole, administrative uses of aircraft accounted 
for 1 1,595 hours in fixed-wing aircraft and" 7,548 hours in helicopters.) 

Managers were then asked what sorts of management activities most often 
employed the use of aircraft. Seven activities were consistendy named by 
managers. Figure 8. 1 identifies these activities. The figure also shows the 
percentage of parks that use aircraft in support of each activity. For each of 
the seven activities, over 50 percent of the parks used aircraft in support of 
the activity during the prior year. The two most frequendy mentioned 
activities were search and rescue, and resource management. [Compared to 
systemwide flying, parks in this sampled subset of parks did more flying for 
fire fighting and law enforcement and less for administrative, maintenance, 
and search and rescue purposes.] 



< 



Most Prevalent Uses of Aircraft 
by Park Management 




Search & Rescue 

Resource Management 

Research 

Fire Fighting 

Administration f: 



20 40 60 80 

Percent of Parks Using Aircraft 



100 



Figure 8. 1 : Most Prevalent Uses of Aircraft by NPS Park Management 



166 



8. 1 Values Associated with Administrative Use of Aircraft 



To ascertain the extent to which aircraft are used for these management 
activities by individual parks, managers were asked to provide the number of 
flying hours their park logged in support of each activity. Figures 8.2 and 8.3 
summarize the manager's responses. Figure 8.2 shows annual helicopter 
flight hours, and Figure 8.3 shows annual fixed-wing flight hours. Each of 
the averages for each management activity were obtained by including the 
hours of just those parks reporting the use of aircraft in support of that 
activity. Hence, for those parks that use helicopters to assist in law 
enforcement, the average reported number of annual flying hours was 27. 
For parks using fixed-wing aircraft for law enforcement, the average number 
of flying hours was 39. It should be noted that in general managers reported 
the overflights by aircraft on park business (for management purposes or 
emergencies) make up a small fraction of all overflights (see Chapter 2, 
Section 2.1.1). 



o 
<. 

c 

0) 

E 



Annual Helicopter Flight Hours 
Flown by Park Management 



Search & Rescue 

Resource Management 

Research 

Fire Fighting 

Administration 

Maintenance 



20 



41 



27 



13: 



:21 



27 



20 



40 60 

Annual Flight Hours 



80 



93 



100 



Figure 8.2: Annual Helicopter Flight Hours Flown by NPS Park Management 



o 

c 
o 
5 



Annual Helicopter Flight Hours 
Flown by Park Management 



Search & Rescue 

Resource Management 

Research 

Fire Fighting 

Administration 

Maintenance 

Law Enforcement 








40 60 

Annual Flight Hours 



Figure 8.3: Annual Fixed Wing Flight Hours Flown by NPS Park Management 



167 



REPORT TO CONGRESS: Values Associated with Aircraft Overflights 



CONCLUSION 8.1: 

NPS managers believe that 

aviation is essential to the 

management of many national 

parks. Parks and visitors benefit 

from the administrative use of 

aircraft for search and rescue, 

science and resource 

management, firefighting, law 

enforcement, maintenance, etc. 



Fire fighting clearly involved the greatest number of flying hours, with 
helicopters rather than fixed-wing showing the bulk of the hours. The 
remainder of the management activities involve substantially less use of 
aircraft. 



8.2 Values Associated with Aerial Tourism 

Historically, air tour passengers have not been formally considered as "park 
visitors." Nonetheless, a large number of people do see Grand Canyon, 
Haleakala, Hawaii Volcanoes, and other national parks from the air. This 
section explores the results of a survey of air tour passengers from the Grand 
Canyon, Haleakala, and Hawaii Volcanoes National Parks (McDonald et al. 
1994). Figure 8.4 shows estimates of annual visitation by land and by air for 
these parks. Bars show the ground visitation (number of people entering the 
park through roadway entrance stations). The other bars show air visitation 
(the number of air tour passenger-trips, to the extent that it can be 
estimated). The figure suggest that a sizable minority of visitors take 
advantage of the opportunity to view these parks, especially the Grand 
Canyon, by air. 



Visitation Access Modes 

Grand Canyon and Hawaiian Parks 



4,000,000 
3,000,000 
2,000,000 
1,000,000 

Ground 




rand 
Canyon 



Hawaiian Parks 



Air Tour 



Access Mode 



Figure 8.4: Relative Visitation Access Modes for Grand Canyon and Hawaiian Parks 



8.2. 1 Tour Passenger Survey Results 

The Air Tour Passenger Survey results must be interpreted with great caution 
because of sampling problems that occurred during the study. During the tall 
of 1 992 a survey of air tour passengers was conducted tor diese three parks. 



168 



8.2 Values Associated with Aerial Tourism 



A questionnaire was mailed to randomly selected passengers after they 
completed their flights. But the extent to which inference can be made to air 
tour passengers over these parks is suspect due to a lack of cooperation by 
major segments of the air tour industry. The manner in which cooperating 
air tour companies collected names (asking for volunteers from their clients 
rather than providing the NPS a complete list of clients from which to 
sample) introduced the possibility of bias in the sample. As a result, the NPS 
abandoned an attempt to survey air tour passenger elsewhere in the country 
during the summer of 1993. The following results from the survey should be 
read and understood in that context. 

Enjoyment and Appreciation of Park. The results of the survey showed 
that overall enjoyment was rated high by most passengers. Figure 8.5 shows 
that over 95 percent of the passengers felt their flights were "moderately," 
"very," or "extremely" enjoyable. Almost 50 percent of the passengers rated 
enjoyment in the "extreme" category alone. 

When asked how much their appreciation of the park had increased as a 
result of their flight, passengers showed similar feelings of enthusiasm. 
Figure 8.6 shows that over 95 percent of the passengers reported their 
appreciation had been increased by a moderate to an extreme degree. When 
asked if they would recommend the flight to others, the trend continued, 
with over 95 percent of the passengers providing positive responses (Figure 
8.7). Perhaps a part of this enthusiasm can be explained by the fact that this 
was the first air tour for most of the passengers surveyed. Figure 8.8 shows 
that over 95 percent of the passengers were experiencing their first air tour 
of a national park. 

Reasons for Taking Air Tours. The survey asked passengers the main 
reason they took an air tour. Figure 8.9 shows that more than one-half of the 
passengers reported the unique perspective afforded by the tour to be the 
primary reason. The second most frequendy mentioned main reason was 
that the air tour afforded a fast means for seeing large expanses of the park. 
The third most frequendy cited reason was the novelty of the air tour. 
Fourth, health or physical disabilities were identified, as well as a variety of 
other reasons. 

The survey also asked passengers about other factors that influenced their 
decision to take an air tour. Figures 8.10, 8.1 1 and 8.12 show the reported 
importance of time constraints, a desire for a unique perspective, and health 
limitations. The unique perspective was the most important reason given for 
making the flight. 



169 



REPORT TO CONGRESS: Values Associated with Aircraft Overflights 



Passenger Response — 
How Enjoyable Was the Flight? 



70 



S 60 



50 ■• •• 



40 



S> 30- 



20 



10 



68 



Grand Canyon 
Hawaiian Parks 




Not at all Slightly Moderately Very 

Passenger Response 



Extremely 



Figure 8.5: Passenger Reports of Air Tour Enjoyment 



Passenger Response — 
Air Tour Increase Park Appreciation? 



60 



50 ■ ■ 



40 ■• 



30- 



£ 20- 



10-- 



I Grand Canyon 
Hawaiian Parks 



Not at all 



Slightly Moderately Very 

Passenger Response 




Extremely 



Figure 8.6: Passenger Reports of Increased Appreciation of Park from Air Tours 



Passenger Response — 
Would You Recommend Flight to Others? 




Grand 
Canyon 



Hawaiian Porks 



Passenger Response 



Figure 8. 7: Passenger Willingness to Recommend Air Tours to Others 



170 



8.2 Values Associated with Aerial Tourism 



Passengers Reporting First Flight 

Grand Canyon and Hawaiian Parks 




Grand 
Canyon 



Hawaiian Parks 



Passenger Response 



Figure 8.8: Percentage of First Time Passengers on Air Tours 



Most Important Reason for Flight 



Other 

$ Health or Physical Disabilities 

o 
a 

2! Experience Unique Activity 

a> 
c 
8! Only Way in Available Time 

£ 

See Park from Unique Perspective 



■s ; 
fir* : 

IP 6 - 






ill! 


Granc 
Hawa 


Cany 
Jan Pa 


Dn 

"ks 


p : 














HP 8 














IHI7: 
















I 16 


f:MM 


111^23 : 














mm i p65 


1 1 


Willi 


Ip3 

1 +-— — 1 



10 20 30 40 50 60 70 
Percentage of Passengers 



Figure 8.9: Passengers' Primary Reasons for Taking Air Tour 



Importance of Flight to Park Enjoyment 

Only Way to See Park in Time Available 



60 



Grand Canyon 
Hawaiian Parks 




Not at all 



Slightly Moderately Very 

Passenger Response 



Extremely 



Figure 8. JO: Importance of Time Constraints as a Reason for Taking Air Tour 



171 



REPORT TO CONGRESS: Volues Associated with Aircraft Overflights 



iportance of Flight to Park Enjoyment 

See Park from Unique Perspective 



60 



50 



40 



30 



20 



10 



64 


^^■i brand Lanyon ££ 
■ Hawaiian Parks 




35 ,o 

M 32 


1 


B 


A 1 

oo ii B 3 | 



Not at all Slightly Moderately Very 

Passenger Response 



Extremely 



Figure 8.11: Importance of Unique Perspective as a Reason for Taking Air Tour 



Importance of Flight to Park Enjoyment 

Overcome Health Limitations 



f. 20 ■• 




Grand Canyon 
Hawaiian Parks 



10 10 



12 



11 



Jtfl 



Not at all 



Slightly Moderately Very 

Passenger Response 



.1.9 

ID 

Extremely 



Figure 8. 12: Importance of Health Limitations as a Reason for Taking Air Tour 

Visiting the Park on the Ground. The findings presented thus tar show- 
reasonable consistency between the Hawaiian parks and Grand Canyon. 
One finding of the survey which was not consistent across the parks was the 
proportion of tour passengers who had (or were about to) tour the park on 
the ground. The results differed significandy. Figure 8.1 3 shows that the 
proportion of Grand Canyon passengers also touring on the ground to be 
about 90 percent. In the Hawaii parks, however, this proportion drops to 
about 30 percent. 

Air tour passengers who were also touring the park on the ground during 
their visit were asked to rate separately the importance ot the air tour and 
the importance of the ground tour to their overall enjoyment of the park. 



172 



8.2 Values Associated with Aerial Tourism 



Figures 8.14 and 8. 1 5, respectively, show the passengers' responses. Over 90 
percent of passengers reported moderate to extreme importance for both 
visitation modes, with little preference for one mode over the other. Neither 
was there a dramatic difference in preference between the Grand Canyon 
and the Hawaiian parks, though the Grand Canyon passengers show a slight 
weighting toward the importance of the ground tour versus the air tour, 
while the Hawaiian passengers report somewhat more importance for the air 
tour. 

Judgments of Impacts to Visitors on the Ground. Finally, passengers 
were asked about their impressions of how disruptive air tour flights were to 
visitors on the ground. Figure 8. 16 shows that approximately 75 percent of 
air tour passengers feel these flights are minimally disruptive ("Not at all" or 
"Slightly"). Only 10 percent expressed the opinion that air tour flights were 
moderately to extremely disruptive. 





Park Visited on Ground Too? 




Grand Canyon and Hawaiian Parks 




o 

CO 

c 

(U 


100 t 














s. 


80 














o 


60 


.••' \/*Zm** 












CO 
D 


40 














c 


20 
t 








M "***>0^ Grand 






p 

o 






\ y^f Canyon 








Yes ~^~^r--Z<^' Hawaiian Parks 








No ^^ 








Passenger Response 





Figure 8. 1 3: Passengers' Plans for Touring Park on the Ground as Well 



Importance of Air Tour to Enjoyment 



Not at a I 




Slightly Moderately Very Much Extremely 

Passenger Response 



Figure 8. 14: Passenger Reports of Importance of Air Tour 
to Overall Enjoyment of the Park 



173 



REPORT TO CONGRESS: Values Associated with Aircraft Overflights 



CONCLUSION 8.2: 

Air tour passengers surveyed 

indicated immense enjoyment 

from their tour experiences, 

would recommend the tour to 

others, and believed it 

increased their appreciation of 

the park. 



Importance of Ground Tour to Enjoyment 



50 



£ 40 



30-- 



§ 20 



£ 10-- 



Grand Canyon 
Hawaiian Parks 




Not at all Slightly Moderately Very Much Extremely 

Passenger Response 



Figure 8. 15: Passenger Reports of Importance of Ground Tour 
to Overall Enjoyment of the Park 



CONCLUSION 8.3: 

Unique perspective and time 

constraints were the most 

important reasons for taking 

flights over parks. Health 

reasons were less important 

though not an insignificant 

consideration. 



Are Flights Disruptive to Visitors on the Ground? 




Not at all 



Grand Canyon 
Hawaiian Parks 



±_,JL o „L 



Slightly Moderately Very Much Extremely 

Passenger Response 



Figure 8.16: Passengers' Assessment of Disruptive Impact 
of Air Tours to Ground Visitors 



CONCLUSION 8.4: 

Air tour passengers over the 
Grand Canyon typically also 

visit that park using ground 
transportation, while those in 
Hawaii do not. 



Figure 8.17 shows passengers' opinions about the tradeoff between the 
benefits of air tours and the disruptive effects they may cause on the ground. 
Passengers were asked to respond to the statement that "Benefits to tour 
passengers outweigh disturbances on the ground." Approximately 30 percent 
gave a neutral response. On either side of neutral, about 55 percent agreed 
or strongly agreed with the statement, and only about 1 5 percent disagreed 
or strongly disagreed. 



174 



Do Air Tour Benefits 
Outweigh Impacts on the Ground? 



S> 30-- 



° 20 ■■ 




Not at all 



Slightly Moderately Very Much Extremely 

Passenger Response 



Figure 8. 7 7: Passengers' Assessment of Whether Air Tour Benefits 
Outweigh Impacts on the Ground 



8.2.2 Are Air Tour Passengers Park Visitors? 

To the extent that these results are accurate, they confirm what tour 
operators assert: most air tour passengers enjoy immensely their tour 
experiences, would recommend such tours to others, and believe the tours 
significandy increased their appreciation of the park. In a sense, these 
passengers enjoy some of the same qualities the park has to offer on-ground 
park visitors. Some air tour operators assert that their passengers are indeed 
park visitors and these operators are proud of their contribution to visitor 
enjoyment of parks. 

But for the NPS, there is a difference. For all ground visitors, the NPS is able 
to regulate numbers and types of visitor activities in the parks in order to 
preserve resources and ensure quality visitor experiences. Numbers of raft 
trips in the Grand Canyon and other parks are limited, with waiting lists of 
many years. 

The number of backcountry use permits issued each year is limited. The 
number of camp sites is limited as are numbers of hotel or lodge rooms or 
cabins. The purpose of these NPS activities is to limit the adverse impacts 
one visitor activity has on others and on the park itself. The purpose of parks 
is to preserve resources and ensure that succeeding generations have a 
chance to experience the same types of opportunities. Anything less is an 
abrogation of NPS responsibility to preserve and protect the parks. 

Air tour operators have consistendy objected to NPS efforts to work with the 
FAA in protecdng park values and resources. They argue that the NPS has no 
right or responsibility to be involved in influencing airspace management. 



8.2 Values Associated with Aerial Tourism 



CONCLUSION 8.5: 

Air tour passengers do not think 
tours cause an impact to visitors 
on the ground. 



175 



REPORT TO CONGRESS: Values Associated with Aircraft Overflights 



They also proclaim that air tours cause the fewest environmental impacts of 
all methods by which the parks may be seen or appreciated, ignoring the fact 
that many air tour passengers impact the park twice — first from the air and 
later when they visit on the ground. 

The NPS perspective is that there are impacts to visitors from aircraft 
overflights, as discussed in Chapter 6. These impacts vary depending upon 
location, visitor activity, aircraft-produced sound exposure, ambient sound 
levels, and other factors, but roughly 30 to 40 percent of Grand Canyon 
backcountry visitors reported moderate to extreme annoyance with the 
sound of aircraft, and 40 to 50 percent reported that the sound of aircraft 
interfered with their appreciation of natural quiet, see Figure 6. 1 . 
Additionally, Chapter 3 showed that, primarily because of the low 
non-aircraft ambient sound levels in parks, even distant aircraft can be easily 
heard. Hence, overflights do produce impacts, both direcdy on visitors as 
well as on the natural quiet resource provided by parks to ground-based 
visitors. 

Perhaps this dichotomy between people who enjoy air tours over national 
parks and people who find that overflights impair their enjoyment of the 
parks is ironically summarized by the responses to one of the questions in 
the Visitors Survey discussed in Chapter 6. Upon being asked how hearing or 
seeing aircraft affected their visit to the park, about 20 percent said they felt 
like complaining to somebody, and about 20 percent said it made them want 
to view the park from the air (McDonald et al. 1 994). 

Air tours do offer access to parks and provide for enjoyment of those parks. 
But the access produces impacts on other visitors and on the park. While the 
NPS has traditionally managed visitor use to conserve the parks and provide 
for their enjoyment by current and future generations of visitors, the FAA 
has sole control over all airspace and over the activities of aircraft owners and 
operators. The NPS and the FAA face two basic choices for dealing widi this 
situation: 

Cooperation: The two agencies can cooperate in reducing the impacts 
of air tours on parks and maintaining the benefits provided by air tours 
in a way that maximizes the safe and efficient use of the airspace. An 
example of this would be an FAA permit process for air tour operations 
utilizing and marketing NPS resources in which die NPS superintendent 
would be required to sign off that the operation was beneficial to park 
visitors and park transportation needs, and/or not an impact to the park 
or park visitors in the locations proposed. 

Legislation: The alternative is that "cooperation" can be legislatively 
accomplished when the problem reaches unmanageable proportions. 
Evidence that some do not have confidence in die ability of die two 



176 



8.4 Values and Impacts of Aerial Filming 



agencies to cooperate is evidenced by three proposals for legislation (See 
Appendix C): 

H.R. 1696: Hawaii Overflight Protection Act, a bill that would 
protect the parks in Hawaii by requiring specified stand-off 
distances and minimum altitude zones over those parks; 

H.R. 4163: National Park Scenic Overflight Concessions Act of 
1 994, a bill to enable the Park Service to regulate, or prohibit, 
scenic commercial overflights at units of the National Park System 
as it does other services provided in parks; 

S. 2428: National Parks Airspace Management Act of 1994, a bill 
that would provide for the regulation of the airspace over National 
Park Service lands in the United States by the FAA in consultation 
with the NPS. 

As a part of this study, a legal review of FAA and NPS authorities was 
conducted (See Appendix D). Between the two agencies, legal authorities 
appear to be adequate to address the impacts identified in this report. So the 
real question is whether and how these authorities are applied to the 
identified impacts. 



8.3 Value of Overflights to Local Economies 

Limited information is available on the economics of air tourism in the 
United States, especially over national parks. It is privileged economic data 
that the FAA does not collect. Based on industry reports, the economic 
impact of Grand Canyon air tours alone is two hundred and fifty million 
dollars ($250,000,000). The industry in Hawaii is apparently very nearly as 
large, and there is a sizable industry in other parts of the country including 
New York, St. Louis, and Southeastern Alaska. The FAA estimates that there 
are at least 1 87 air tours operators across the nation. This suggests the total 
economic impact of the industry is in the range of one-half to three-quarters 
of a billion dollars a year. 



8.4 Values and Impacts of Aerial Filming 

A substantial amount of aerial filming is completed in units of the National 
Park System, although again, there is no readily accessible information on its 
extent. The NPS tends to be responsive to filming requests of all types that 
are non-degrading to the parks or the visitor experience. Yet it is worth 
noting that overflight impacts can occur as a result of these activities as well. 
An example is illustrative. 



177 



REPORT TO CONGRESS: Values Associated with Aircraft Overflights 



In October, 1993, a regional film company was issued a commercial film 

permit to make an IMAX-style film that focused heavily on one of the 

national parks in Utah. In order to protect park values of silence and solitude 

and to protect threatened and endangered species, the permit from the park 

contained a stipulation that no filming by fixed wing or helicopter would be 

allowed. A $25,000 performance bond was posted and then returned when 

the filming was completed. In early March, 1994, park rangers noted 

unauthorized filming by this same company over the park and surrounding 

areas using helicopters. The park had no legal recourse since neither NPS 

r 
nor FAA regulations were broken. Nonetheless, the park considers the 

disregard of permit conditions in the filming permit to be an example of an 

abuse that should not be permitted to continue. [The FAA is initiating a 

change to internal policy regarding issuance of waivers dealing with movie 

production as a result of the Zion incident]. 



8.5 Summary 

National parks and park visitors benefit from the use of aviation: visitors are 
aided through search and rescue flights; parks and the nation benefit from 
fire fighting's use of aircraft; and aviation aids research, resource 
management, and law enforcement in parks. Air tour passengers also benefit 
from aviation. Passengers find their experiences to be very rewarding, both 
in terms of overall enjoyment as well as in providing an. enhanced 
appreciation for the park. Aviation is also a major economic factor in some 
places, most notably around the Grand Canyon and in Hawaii. However, the 
potential exists for expanded operations in many parks. 

Perhaps the most important conclusion, though it must be inferred, is the 
likelihood that there will be increasing airspace issues over the National Park 
System. The high degree of satisfaction with air tours expressed by 
passengers, the willingness of tourists to spend the money for air tours, and 
regulations that provide FAA with sole authority to control airspace use, all 
suggest that air tour operations will increase, while the NPS will continue to 
live with the consequences — until a cooperative process is developed for 
limiting the impacts produced by these overflights. The NPS concludes that a 
process, binding upon all parties, must be designed and implemented to 
identify, measure and limit overflight produced problems in units of the 
National Park System. Voluntary agreements may be part of this process, but 
they cannot stand alone because of their limited effectiveness. 



178 



^%^ 



9 



RESTORATION OF NATURAL QUIET 

Section 2 of the National Parks Overflights Act (P.L. 100-91) set specific 
minimum altitude requirements for aircraft overflights of Yosemite and 
Haleakala National Parks. The intent of the law was to determine the extent 
to which minimum altitudes for overflights could restore natural quiet. Prior 
to the passage of the Act, aircraft had been reported flying within a few 
hundred feet of the ground in these two parks. Hence, increasing the 
minimum distance above the terrain to 2,000 feet in Yosemite, and almost 
the same amount in Haleakala, should produce a noticeable difference in the 
aircraft sound environment, even if not fully restoring natural quiet. 

Section 3 of the Act discusses the aircraft overflights issue at Grand Canyon 
National Park (GCNP). That section states that: 

fo) "Noise associated with aircraft overflights at the Grand 
Canyon National Park is causing a significant adverse effect on 
the natural quiet and experience of the park. ..." 

This section further states that recommendations submitted to the 
Administrator of the Federal Aviation Administration (FAA) would: 

"provide for substantial restoration of the natural quiet and 
experience of the park and protection of public health and 
safety from adverse effects associated with aircraft overflight. " 



179 



REPORT TO CONGRESS: Restoration of Notural Quiet 



The Section then states that: 

*. . . the Secretary [of Interior] shall submit to the Congress a 
report discussing — (AJ whether the plan has succeeded in 
substantially restoring the natural quiet in the park;. . . ." 

The following sections contain the NPS response to the questions posed in 
Sections 2 and 3 of the Act. 



9.1 Report on Section 2 Requirements — 
Yosemite and Haleakala National Parks 

9. 1 . 1 Yosemite National Park 

"Sec. 2(a) Yosemite National Park — During the study and 
review periods provided in subsection^(c), it shall be unlawful 
for any fixed wing aircraft or helicopter flying under visual flight 
rules to fly at an altitude of less than 2,000 feet over the surface 
of Yosemite National Park. For purposes of this subsection, the 
term "surface" refers to the highest terrain within the park 
which is within 2,000 feet laterally of the route of flight and 
with respect to Yosemite Valley such term refers to the 
upper-most rim of the valley." 

In Yosemite, management reported the major complaints about overflights 
came from wilderness trail users (at higher elevations of the park), as 
opposed to visitors on the valley floor. Management felt that the minimum 
altitude requirement had helped significandy in reducing complaints. This 
has not meant a restoration of natural quiet. The sample of acoustic 
measurements made in Yosemite in 1993, Figure 2. 17 part 3, showed 
aircraft to be audible 30-60 percent of the time. Regarding compliance, 
management felt that pilots who were aware of the restriction generally 
complied with the law. 

Measurements were made at four sites in Yosemite: Rafterty Creek (judged 
to be a location where visitors have a high expectation of experiencing 
quiet); Soda Springs Road (higher expectation of quiet than in the valley, but 
fairly congested with a nearby campground store area and concessionaire 
stables); Mirror Lake (only part of the valley floor that is closed to traffic, but 
traffic noise from the rest of the valley is audible); Glacier Point (one of most 
popular destinations in park and often crowded, with voices audible). In 
general, high altitude jets were the most commonly audible aircraft heard at 
the rate of about 10 to 30 per hour. Private propeller airplanes (general 
aviation) were heard at the rate of about two to four per hour. 



180 



9.2 Report on Section 3 Requirements: Grand Canyon National Park 



9. 1 .2 Haleakala National Park 

"Sec. 2(b) Haleakala National Park — During the study and 
review periods provided in subsection (c), it shall be unlawful 
for any fixed wing aircraft or helicopter flying under visual flight 
rules to fly at an altitude below 9,500 feet above mean sea 
level over the surface of any of the following areas in Haleakala 
National Park: Haleakala Crater, Crater Cabins, the Scientific 
Research Reserve, Halemauu Trail, Kaupo Gap Trail, or any 
designated tourist viewpoint." 

Prior to passage of PL 100-91, management reported that commercial tour 
helicopters flew within the crater down to levels 300 feet above the crater 
floor. Noise generated by tour helicopter overflights gready impacted the 
wilderness users' enjoyment of Haleakala Crater. Management further stated 
that Haleakala was famous for its natural quiet, but this quality deteriorated 
as overflights increased. 

Management felt that the altitude restriction of PL 1 00-9 1 somewhat 
reduced the noise levels on the crater floor. However, since the passage of 
the Act, the number of overflights has increased significantly, thus negating 
improvements the restriction might have made. Acoustic measurements 
made at four sites in Haleakala in 1992, Figure 2.17 part 3, showed that 
aircraft were audible 38-76 percent of the time. Aircraft heard were 
predominandy helicopters, heard at rates of about eight to ten per hour 
(Anderson etal. 1993, Horonjeff et al. 1993) 



9.2 Report on Section 3 Requirements: 
Grand Canyon National Park 

This section provides for the definition of a substantial restoration of natural 
quiet, an explanation of SFAR 50-2, the description of the studies used in 
the evaluation, and the conclusions reached. It is important to note that 
during the course of these evaluative studies, air tours have increased 
significandy over the Canyon. Existing and forecast operations at the Grand 
Canyon National Park Airport are a useful indicator of the trends in 
increasing overflights. For example in 1987, there were 120, 180 operations 
at that airport alone. In 1993, operations at the airport were 187,444, 
already exceeding those forecast in the airport master plan for the year 2000. 
By the year 2010, 240, 1 00 operations are forecast. It is vital that this 
evaluation of Special Federal Aviation Regulation (SFAR) 50-2 be 
understood in the context of this growth pattern. 



CONCLUSION 9.1 

The lessons learned from 
Yosemite and Haleakala may 
be summarized as follows: 

• Raising the minimum altitude 
to 2,000 feet (the long standing 
FAA advisory altitude for 
overflying parks) reduces 
egregious impacts and may 
reduce complaints, but does not 
effectively restore natural quiet. 
Not only are the lower altitude 
aircraft audible, but 
high-altitude jets and the sound 
levels they produce are 
unaffected by such minimum 
altitudes. Nevertheless, a 
2000-foot minimum altitude 
can be effective in limiting 
some adverse effects on natural 
quiet. 

• Numbers of overflights have 
an important impact on length 
of time visitors have an 
opportunity to experience 
natural quiet. Unabated 
increases in numbers can 
negate gains made through 
increasing the distance 
between aircraft and visitors. 

• As part of their management 
strategy, park resource 
managers must carefully 
consider when and where to 
preserve natural quiet, devising 
management strategies for FAA 
action. 

• Impacts on natural quiet are 
likely to be unique at each 
park, and the solutions equally 
unique. Approaches to problem 
solving need to be flexible to 
produce effective solutions. 



181 



REPORT TO CONGRESS: Restoration of Natural Quiet 



CONCLUSION 9.2 

A substantial restoration of 

natural quiet in the Grand 

Canyon will require that there 

be natural quiet in halt or more 

of the park for most of the day. 



9.2. 1 Defining a Substantial Restoration of Natural Quiet 

Before overflights began, natural quiet existed over most of park, virtually all 
of the time. Aircraft sound intrusions are a significant source of mechanical 
noise that eliminate natural quiet. Since the legislative history of Public Law 
1 00-9 1 indicates that flight-free zones are to be large areas where visitors can 
experience the park essentially free from aircraft sound intrusions, and 
where the sound from aircraft traveling adjacent to the flight-free zone is not 
detectable from most locations within the zone, the primary measure of 
restoration is the percentage of time that aircraft are audible. Based on this 
definition from the legislative history, the policy decision of Grand Canyon 
National Park (GCNP) is that a substantial restoration requires that 
50% or more of the park achieve "natural quiet" (i.e., no aircraft 
audible) for 75-100 percent of the day. 



9.2.2 Special Federal Aviation Regulations 50-2 

The NPS and the FAA have attempted through SFAR 50-2 to accomplish the 
substantial restoration of natural quiet. The regulation established flight-free 
zones and specific flight corridors and routes for air tours and general 
aviation flights. It also established minimum altitude restrictions on all types 
of flights including air tours, general aviation, high altitude commercial and 
military aircraft (see Figure 9. 1). 

Design and implementation of SFAR 50-2 was a major accomplishment in 
that it is the first attempt by the FAA to regulate airspace for environmental 
and safety reasons to such an extent over a national park. Four flight-free 
zones cover 45% of the park and have a ceiling of 14,499 feet Mean Sea 
Level (MSL). Four flight corridors were established to help aircraft navigate 
the Special Use Airspace while avoiding the flight-free zones. Approximately 
29 aerial tour routes were created by the Federal Aviation Administration's 
Flight Standards District Office in Las Vegas to allow commercial tour 
aircraft access to that portion of the Special Flight Rules Area (55%) not 
restricted by flight- free zones. [At 14,500 feet MSL the entire park is 
accessible to overflights] . v 

9.2.3 Evaluation of Restoration Efforts (SFAR 50-2) 

The determination as to whether SFAR 50-2 has been effective in 
substantially restoring natural quiet is based on a series of studies and 
modeling exercises. Among the questions asked are: Do its flight- free zones 
and altitude restrictions substantially restore natural quiet? How effective is 
the SFAR? Are there areas where improvements are possible? 



182 




OH9) 



183 



REPORT TO CONGRESS: Restoration of Natural Quiet 



Management Objectives 

First, the NPS reviewed its mandates, regulations, policies, and plans related 
to the protection of natural quiet and the provision of various visitor 
experience opportunities. From this review, a statement of management 
goals and objectives was developed to further assist in the evaluation of the 
effectiveness of SFAR 50-2. This statement describes the goals and Table 9. 1 
summarizes the specific management objectives for each of five management 
zones in the park. 

Goals for aircraft overflight management listed in the GCNP's policy paper 
are: 

1 . Substantially restore natural quiet as a natural resource. 

2. Provide recreation opportunities and experiences for park 
visitors, consistent with park policies, where the opportunity for 
natural quiet is an important component. 

3. Mitigate any aircraft-related impacts on other natural and cultural 
resources. 

4. Address issues of health, safety and welfare of on-ground visitors 
and employees. 



TABLE 9.1 GRAND CANYON NATIONAL PARK MANAGEMENT OBJECTIVES 


OBJECTIVE 


PERTINENT ZONE(S) 


a. Restore and maintain natural quiet by protecting the wilderness character 
of remote areas. 


Backcountry Use Zone 
River Corridor Use Zone 


b. Provide primitive recreation opportunities without aircraft intrusions in 
most backcountry areas, most locations on the river and at destination points 
accessed by both. 


Backcountry Use Zone 
River Corridor Use Zone 
Corridor Trail System Use Zone 


c. Provide developed recreation opportunities with limited aircraft intrusions 
for visitors at rim developed areas and major frontcountry destination points 
accessible by road. 


Frontcountry (Paved Access) Use Zone 


d. Provide for protection of sensitive wildlife habitat areas or cultural 
resources. 


Backcountry Use Zone 
River Corridor Use Zone 
Corridor Trail System Use Zone 
Frontcountry (Paved Access) Use Zone 


e. Provide for welfare and safety of below-rim, backcountry, and rim visitors. 


Backcountry Use Zone 
River Corridor Use Zone 
Corridor Trail System Use Zone 
Frontcountry (Paved Access) Use Zone 


f. Provide a quality aerial viewing experience while protecting park resources 
(including natural quiet) and minimizing conflicts with other park visitors. 


Air Tour Use Zone 
Backcountry Use Zone 
River Corridor Use Zone 
Corridor Trail System Use Zone 
Frontcountry (Paved Access) Use Zone 



184 



9.2 Report on Sect/on 3 Requirements: Grand Canyon National Park 



Evaluation 



The evaluation of the restoration of natural quiet is based on the following 
six categories of studies, monitoring, and modeling exercises. 

1 . GCNP's Monitoring and Visitor Complaints: The NPS has 

considered information provided by visitor complaints and by the park's 
aircraft monitoring program. Although complaints have been reduced in 
number since SFAR 50-2, complaints received now focus on specific areas. 
That is, complaints are usually correlated to areas that are impacted 
acoustically which are generally located below the rim. Arguments have been 
made that the reduction in complaints means that natural quiet has been 
substantially restored. Even though the NPS values visitor complaints and 
uses them to help confirm problem areas, a relationship cannot be drawn 
between reduction in complaints and the restoration of natural quiet, which 
must be acoustically determined. Congress did not request a substantial 
reduction of visitor complaints; the NPS manages parks to protect resources 
rather than simply respond to visitor complaints. 

The monitoring program logs flights on a yearly basis to determine aircraft 
use along routes and compliance with the regulation. Monitoring data 
provide additional confirmation regarding areas of heavy aircraft activity over 
areas with popular on-the-ground use. For instance, the Hermit Trail, which 
lies under the Dragon Flight Corridor, was found to experience an average of 
3 5 aircraft overflights per hour. With aircraft passing over any number of 
points along the trail at this frequency, the sound of aircraft can be constant. 
Other "areas of concern" include Point Sublime, also under the Dragon 
Corridor; Point Imperial, the Nankoweap trail and the mouth of the Little 
Colorado River, under the Zuni Point Flight Corridor routes; and the 
Toroweap Overlook, close to eastbound routes from Las Vegas. 

Results of the monitoring confirm an extremely high rate of compliance by 
air tour operators and other aircraft users flying over the area. The 
compliance is a compliment to the managers and users of the airspace over 
Grand Canyon. 

2. Acoustic Monitoring Study: Acoustic monitoring was conducted at 23 
sites in the Canyon during August and September of 1992 (Horonjeff et al. 

1 993). Sites were chosen on the north and south rims and along the river, 
under both flight corridors and flight-free zones, and Figure 9.2 shows 
where these sound level measurement sites were located. 

The data were collected in a manner that yielded not only decibel levels, but 
information about the amount of time aircraft overflights could be heard at 
each site. A detailed analysis of the data provides estimates of the percentages 
of time the aircraft of various operators could be heard (Robert et al. *). 
Tables 9.2 and 9.3 present the results from the monitoring. At most sites 



CONCLUSION 9.3 

Flight-free zones can limit the 
areas where aircraft, especially 
tour aircraft, are audible high 
percentages of the time. But 
aircraft of all types may still be 
heard for some percent of the 
time at virtually all areas where 
sound data were collected, 
notably within a few miles of 
the edges of some of the 
flight-free zones. These results 
suggest that a substantial 
restoration of natural quiet has 
not been achieved for large 
segments of the Canyon. 



185 



REPORT TO CONGRESS: Restoration of Natural Quiet 




Figure 9.2: Grand Canyon National Park Acoustic Monitoring Sites 



186 



9.2 Report on Section 3 Requirements: Grand Canyon National Park 



under flight-free zones, aircraft were audible for lower percentages of the 
time than was the case under the flight corridors. Generally, within 
flight-free zones (Phantom Ranch, Bright Angel Point, Yaki Point), tour 
aircraft were audible ten percent of the time or less, while near the edges 
(Desert View, Lipan Point, Point Sublime), these aircraft were audible for 
considerably greater amounts of time. Commercial jets (high altitude 
overflights) were generally audible less than about 1 5 percent of the time, 
but could be heard at most locations. Very few general aviation or military 
aircraft were heard. 

3. Dose-Response Studies: In order to quantify how visitors feel about 
the sound of aircraft overflights, the NPS conducted data collection of a type 
never before done in a recreational setting: "dose-response" measurements. 
Simultaneous measurement of aircraft sound levels and surveys of visitors 
permitted development of "dose-response" relationships that estimate what 
percent of people are affected by a given amount of aircraft overflight sound 
(Anderson et al. 1993). Only in residential communities have such data ever 
been acquired,and never with such close coordination between the measured 
"dose" of sound that was present and the individual responses. Extreme care 
was taken in the data collection and analysis, and some specific conclusions 
are possible. 



TABLE 9.2: PERCENT OF TIME AIRCRAFT WERE AUDIBLE 


Site 
Number 

(See 
Fig. 9.2) 


Description 


Measured 

Percent of Time 

Aircraft are 

Audible* 


Estimated Percent of Time 
Aircraft are Audible by Operator 


Tour 


Comm Jet 


G/A 


Military 


Desert View Flight-free Zone 






12.0 


Desert View 


20 


14 


6 


1 


17.0 


Lipan Point 


43 


30 


14 


1 


Bright Angel Flight-Free Zone 


2.1 


Phantom Ranch Overlook (Edge) 


19 


7 


11 








2.2 


Phantom Ranch Overlook 


11 


8 


4 








10.0 


Bright Angel Point 


20 


6 


13 


1 





18.0 


Yaki Point 


12 


5 


7 








Shinum 




t?S|:;j 






9 Flight-Free Zone 




...' :■:.■.■.:: ..\ 


19.0 


Point Sublime 


76 


69 


12 





1 


20.0 


1 17.4 Mile Camp 


4 





4 





1 


Toroweap/Thunder Rrver Plight-Free Zone 


6.1 


Deer Creek Falls 


9 


2 


7 








6.2 


Deer Creek Falls (1/2 Mi. NE) 


7 


4 





3 





14.0 


Toroweap Overlook 


54 


44 


11 





1 


* The measured percent of time audible will not always equal the sum of percents by operator because aircraft of different 
operators were sometimes audible at the same time. 



187 



REPORT TO CONGRESS: Restoration of Natural Quiet 



TABLE 9.2: PERCENT OF TIME AIRCRAFT WERE AUDIBLE (continued) 


She 
Number 

(See 
Fig. 9.2) 


i 

Description 


Measured 

Percent of Time 

Aircraft are 

Audible* 


Estimated Percent of Time 
Aircraft are Audible by Operator 


Tour 


Comm Jet 


G/A 


Military 


Dragon Flight Corridor 


3.0 


96 Mile Camp 


52 


51 


1 








16.0 


Hermit Basin 


83 


79 


18 


1 





Fossil Canyon Flight Corridor 






5.0 


Stone Creek Camp 


6 


2 


4 








7.0 


Havasu Creek 


12 


9 


1 


2 





Areas Under Minimum Attitude Zones 






1.0 


Marble Canyon 


13 


5 


7 








31.0 


Marble Canyon / Buck Farm 


7 


1 


6 








13.0 


Little Colorado River 


50 


47 


3 








15.0 


Pt. Imperial 


66 


61 


"8 


1 





8.0 


Whitmore Rapids 


20 


20 


1 








23.0 


Diamond Creek 


13 


7 


2 





4 


9.0 


Separation Canyon 


20 


16 


3 








21.0 


Burnt Springs Canyon 


50 


48 


3 








* The measured percent of time audible will not always equal the sum of percents by operator because aircraft of different 
operators were sometimes audible at the same time. 



CONCLUSION 9.4: 

The percent of time aircraft are 

audible correlates with how 

visitors feel about aircraft 

sound. Even when aircraft are 

audible for relatively low 

percentages of time, a 

percentage of the visitors can 

notice the aircraft, and believe 

that the sound has interfered 

with their appreciation of 

natural quiet. Further, it is likely 

that visitors who hike away 

from auto accessible locations 

are more sensitive to intruding 

aircraft sounds than are visitors 

who do not. Hence, the NPS 

concludes that preservation of 

natural quiet is of significant 

value to visitors, especially for 

the backcountry, river corridor 

and Cross Canyon Corridor trail 

system use zones at GCNP. 



For overflights of tour aircraft, the measure of sound that best predicts 
visitors' reactions is the percent of time aircraft are audible. The results show 
that visitors have very different sensitivity to aircraft sound, depending upon 
the site where data are collected. At the two frontcountry "overlook" sites, 
Lipan Point and Point Imperial, for a given level of aircraft sound, 
considerably fewer visitors reported annoyance or interference with natural 
quiet than reported these effects at the three "short-hike" sites of Hermit 
Basin in the Grand Canyon and Sliding Sands and Wahaula Temple in 
Hawaii. Though many factors likely influence this sensitivity, it is reasonable 
to conclude that as visitors pursue activities that take them away from their 
cars and other visitor activities, they are likely to be more sensitive to the 
sound of aircraft overflights — tour aircraft in the case of this study. For 
visitors to the short-hike sites, roughly 30 to 40 percent can be expected to 
report moderate to extreme interference with their appreciation of natural 
quiet when aircraft are audible ten percent of the time . 



I . See (Anderson, G.S., el at, 1993) Figure E. 3 or Figures H.8 and H.9. 



188 



9.2 Report on Section 3 Requirements: Grand Canyon National Park 



4. Bennett-Cox Study: The Air Access Coalition (an association of air tour 

operators) retained Bennett/ Cox, Consultants, to sample sound exposure at 

22 sites before (in 1988) and after (in 1993) SFAR 50-2 was implemented 

over the Grand Canyon (Bennett et al. 1994). The consultants used methods 

that permitted separate identification of maximum sound levels for different 

aircraft types and ranges of non-aircraft sound levels. One of the 

measurement sites chosen, Point Sublime, was also a site where NPS had 

2 
acoustic information collected in September 1992 . The Bennett/ Cox data 

show considerable reduction of (maximum) A-weighted sound levels trom 

1988 to 1993, attributable to SFAR 50-2. In fact, the Bennett/ Cox 1993 

aircraft sound levels are entirely consistent with the NPS NPOA Report No. 

93-4 levels for Point Sublime, and the NPS acknowledges that SFAR 50-2 

has produced significant reductions in aircraft sound levels for this location. 

The Air Access Coalition would like to use 1988 sound levels as a baseline to 

compare changes in sound levels; 1988 was already too noisy for the NPS 

which uses natural quiet as the baseline for comparison. 

However, the Bennett/ Cox presentation fails to report two other important 
aspects of the Point Sublime sound environment, one an omission, one 
probably an error. First, the presentation gives no account of how much of 
the time aircraft could be heard or how many were heard. Over 
approximately a five-hour period, the NPS data report roughly 20 to 30 
aircraft per hour were heard, and aircraft were audible an average of 76 
percent of the time (See Table 9.2). Second, Bennett/ Cox report the 
non-aircraft background sound levels as between approximately 20 and 40 
dBA. Though such background levels are certainly possible, particularly if 
there was fairly continuous wind or bird and insect sounds, it is likely that 
the equipment used was not capable of accurately measuring the low sound 
levels present at this location. During the NPS-sponsored measurements, 
non-aircraft sound levels were between approximately 10 and 20 dBA 
roughly 75 percent of the time when aircraft were not audible. Standard 
sound measuring instrumentation used in community noise measurements 
will not accurately measure below 20 to 25 dBA. Special "low-noise" 
instruments were designed and constructed for the NPS measurements 
(Horonjeff et al. 1993) . Thus, though the Bennett/ Cox presentation 
reasonably depicts the changes in (maximum) aircraft sound levels, it fails to 
address two aspects of the sound environment that are critical for judging the 
restoration of natural quiet: the extreme quiet present at some locations, and 
the amount that this quiet is disrupted by the sound of aircraft overflights. 



CONCLUSION 9.5: 

The Air Access 
Coalition-sponsored data 
demonstrate that SFAR 50-2 
has reduced aircraft sound 
levels significantly at some 
locations. However, these data 
do not address restoration of 
natural quiet, since no 
information is given about how 
much of the time aircraft can be 
heard, and reported 
non-aircraft sound levels are 
probably inaccurately high. 



2. Site / 9.0 reported in NPOA 93-4, page I SOff. 

3. See page 9 and NPOA Report 93-6, Appendix CJor descriptions of the instrumentation used. 



189 



REPORT TO CONGRESS: Restoration of Natural Quiet 



CONCLUSION 9.6: 

For some categories of visitors, 

specifically river users and fall 

backcountry visitors, natural 

quiet is almost as important a 

reason for visiting the Grand 

Canyon as is viewing the 

scenery. Enjoying natural quiet 

is extremely important to many 

visitors to the Grand Canyon. 



5. Visitor Survey: A mail survey was conducted of randomly sampled 
visitors to the Grand Canyon. These visitors were separately identified in five 
categories: frontcountry visitors, summer and fall backcountry visitors, river 
users in motorized boats, and river users in oar-powered boats (Baumgartner 
et al. 1994). Figures 9.3 and 9.4 show how these visitors ranked various 
reasons for their trip to the Canyon. Visitors were asked to rate (not 
important at all, si ightly important, moderately important, very important, 
extremely important) eight different reasons . Five of these categories 
(representing the range of responses) are shown in Figures 9.3 and 9.4. 
Figure 9.3 shows the percent who rated the reasons as moderately, very or 
extremely important. Clearly, all these reasons are important in this figure. 



Visitor Reports of Reasons for Visit 

(Moderately to Extremely Important) 



o 

Q) 





1: 




___________________ 1 


Exercise 


1 






















Learning 


1 






• J 










" 




-_„___________-, 




Family Activity 




















1 




Natural Quiet 


T^ ~^~~' : ■:- ■ - ..;. ■ 'l 














View Scenery 









10 20 30 40 50 60 70 80 90 100 
Percent Reporting as Important 



Frontcountry 
1^ Summer Backcountry 
Fall Backcountry 



\'S.r\ River: Motor 
I River: Oar 



Figure 9.3: Visitor Reports of Reasons for Visiting the Canyon 

However, Figure 9.4 shows just those who rated the reasons as extremely 
important. Natural quiet, for river and fall backcountry visitors is almost as 
important as viewing the scenery, while the other reasons are less important. 



4. View the natural scenery, enjoy the natural quiet, appreciate the history and/or cultural significance of the park, do things mthjamily, experience peace 
and quiet, see new and different things, learn about things in the park, get some physical exercise. 



190 



9.2 Report on Section 3 Requirements: Grand Canyon National Park 



Visitor Reports of Reasons for Visit 

(Extremely Important) 



Exercise 



Learning 



!_ Family Activity 
o 



Natural Quiet 



View Scenery 




10 20 30 40 50 60 70 80 90 100 

Percent Reporting as Extremely Importcnt 



Frontcountry r,S A River: Motor 

Summer Backcountry I River: Oar 



ililli Fall Backcountry 



Figure 9.4: Visitor Reports of the Most Important Reasons 



Of these different categories of visitors, how many reported hearing aircraft? 
Figure 9.5 gives the percentages. For all categories, half or more than half of 
the surveyed visitors remembered hearing aircraft. Figure 9.6 (identical to 
Figure 3.4) shows what percentages of these visitors reported moderate, very 
or extreme impacts from the overflights. 

Figure 9.7 shows how inappropriate the five categories of visitors thought six 
different types of overflights to be when within hearing or sight of visitors. 
Clearly, most visitors find military training and private aircraft somewhat or 
very inappropriate over National Park areas. Tour aircraft overflights and 
"transporting commercial passengers between cities" are judged 
inappropriate by roughly comparable percentages of visitors, depending 
upon visitor category. Finally, few visitors judge park "management, 
research, and maintenance" or "emergency services, like fire fighting or 
search and rescue" as inappropriate. 



CONCLUSION 9.7: 

Different categories of visitors 
report different degrees of 
adverse effects, but for all 
categories sampled, more 
visitors report that aircraft 
interfere with their appreciation 
of natural quiet than report 
interference with enjoyment or 
annoyance. 



CONCLUSION 9.8: 

Except for park management 
and emergency-related 
overflights, large percentages 
of Grand Canyon visitors 
regard aircraft overflights 
within sight or hearing of 
visitors on the ground as 
somewhat or very inappropriate 
over National Park areas. 



191 



REPORT TO CONGRESS: Restoration of Natural Quiet 



Visitor Reports of Hearing Aircraft 

By Type of Visitor Activity 



Frontcountry 

























mer Backcountry 




















Fall Backcountry 






. 












River: Motor 




















River: Oar 


1 1 1 1 1 1 1 1 



10 20 30 40 50 60 70 80 90 100 
Percent Reporting Hearing Aircraft 



Figure 9.5: Visitor Reports of Hearing Aircraft 



Frontcountry 

Summer Backcountry 

Fall Backcountry 



a River: Motor 



Visitor Reports of Impacts 

By Type of Visitor Activity 



River: Oar 



GRAND CANYON 






^L 



■— "" . - ■ ■- ■-■-..■■■■■.,: — ^1 



10 20 30 40 50 60 70 80 90 100 
Percent Reporting Impact 

I ^Interference with Enjoyment \£&3 Annoyed H Interference with Naturol Quiet 



Figure 9.6: Visitor Reports of Imparts 



CONCLUSION 9.9: 

There is little support among 

the five categories of Grand 

Canyon visitors for a "do 

nothing" policy or a 

"reasonable growth" policy. 

Maintenance of the current 

level, or reduction/elimination 

are preferred policies. 



The mail survey asked: 

"Considering ihe advanfages and disadvantages of aircraft 
flying over National Park areas, what do you think the National 
Park policy should be for aircraft activity for the following 
aircraft flight purposes?" 

Figure 9.8 presents the responses tor "sightseeing tour flights". The great 
majority of respondents neither support "reasonable growth" nor "do 
nothing." They want to see the activity stay at current levels or be 
reduced/eliminated. Virtually all of the river/oar and fall backcountry visitors 
support reduction or elimination of sightseeing tour flights. 



192 



9.2 Report on Section 3 Requirements: Grand Canyon National Park 



Inappropriateness of Overflights 

(Somewhat or Very Inappropriate) 



Emergency 



Management 



■£ Commercial 




o 

a 



Tour 



Private 



Military 



; l i'^'r;; ■,.... ■ ": ■ r ...... ^/^^^J 



I^HHMHBH 



S3-. 



■■■■■■■r iVi.iiii i...y.i....-i»j :: ■; ■■■■■■-------■-■.■■■--■■ --J 



mmmmm 



'» "" > "") » ""<"" l ) ii'i»' "H""t l' " » "">""»"", |l " 






> H I H i ■ ■ H W I ■ ■ | H I !■■ « » ■ ■ 1 1> ■ ■ I ■« i mm illl H III H (.. ^ (^yMy 



10 20 30 40 50 60 70 80 90 100 
Percent Reporting as Inappropriate 



J Frontcountry Y /" A River: Motor 

~--ZA Summer Backcountry ' I River: Oar 



plfpl F°H Backcountry 



Figure 9. 7: Inappropriateness of Overflights 



Finally, the survey asked:. 

"If aircraft activity got to the point where restrictions were 
thought to be necessary on aircraft flights over a National Park, 
how much would you support each of the following . . . 
restrictions on sightseeing tour flights?" 

Figure 9.9 shows percentages of visitors, by visitor category, who support or 
strongly support seven types of limitations. Visitor support varies with visitor 
category, but over half of all visitors would support encouraging the use of 
quieter aircraft, restricting the number of flights that are permitted to fly 
over the park, establishing times of the day when aircraft are not permitted 
to fly over the park, establishing areas in the park where aircraft are 
prohibited, as well as areas where they are allowed to fly. 

6. Acoustic Modeling/ Quiet Aircraft Study: Computerized acoustic 
modeling is a commonly used approach to depict sound levels or sound 
exposure over large geographic areas. On-site sound measurements are 



CONCLUSION 9.10: 

A majority of visitors to the 
Grand Canyon would support 
several specific types of 
limitations on air tour 
overflights. 



193 



REPORT TO CONGRESS: Restoration of Natural Quiet 



Visitor View of Park Overflight Policy 

Support for Policies Toward Air Tours 



Reduce or 
Eliminate 




No Effort 
to Change L 



10 20 30 40 50 60 70 80 90 100 
Percent of Visitors Supporting 



| | Frontcountry 

pZ-Zj Summer Backcountry 
ill Fall Backcountry 



River: Motor 
River: Oar 



Figure 9.8: Visitor View of Park Overflight Policy 



CONCLUSION 9.11: 

Computer modeling supports 

the conclusion that natural 

quiet has not been substantially 

restored, that very few areas 

currently experience natural 

quiet, and that the areas of 

natural quiet will diminish 

considerably if no quiet aircraft 

are introduced and if tour 

operations are permitted to 

increase. The acoustic profiles 

tend to verify the computed 

results. 



expensive, generally difficult, time consuming, and can be conducted at only 
a few specific locations, hence computer modeling of sound exposure is 
necessary in order to understand sound levels area-wide. The NPS sponsored 
development of a computer model (the National Park Service Overflight 
Decision Support System or NODSS) (Reddingius 1994) that can calculate 
various sound metrics across parks, including time-above a specified 
threshold (e.g. natural quiet). The program computes sound levels for large 
areas of a park, using information about types, numbers and altitudes of 
aircraft flown, locations of flight tracks and geographic terrain information. 
The results of the computations included in this report can be interpreted in 
terms of "natural quiet" (white), areas where natural quiet has been 
"substantially restored" (green), and "remainder of park"(red), and hence 
provide a visualization of the status of natural quiet in GCNP. 

Using the numbers, routes, altitudes, and equipment types indicated in a 
1989 FAA survey conducted on behalf of the NPS, the NODSS modeling 
software produced Figure 9.10 (1989 Levels). The combined colors of white 



194 



9.2 Report on Section 3 Requirements: Grand Canyon National Park 



Visitor Support for Overflight Limits 

Support for Limits on Air Tours 









----- ----------- -.| 
















= 1 , 


Limit Number 
















Higher 




jp .j^^j^i 


c 
o 






i 




---------- 


c Seasons 















i 


9- Days of Week 


-_-_-_-_-_-_-_-_-_-_-_i 




.b ' 










= jJ 


Times of Day 






^^■■■^ ' 








l 




....rr,.^,^^ 







10 20 30 40 50 60 70 80 90 100 
Percent of Visitors Supporting 



Frontcountry r .' f ".=M River: Motor 

Summer Backcountry I River: Oar 

Fall Backcountry 



Figure 9.9: Visitor Support for Overflight Limits 



and green cover about 34% of the park (white is 0.49% and green is 
33.94%). If no quiet aircraft are introduced, and operations continue to 
increase as forecast in the Grand Canyon National Park Airport Master Plan, 
Figure 9. 1 1 results (20 1 No Action). This figure graphically depicts the 
progress lost in the restoration of natural quiet that could occur by the year 
2010 if conditions remain unchanged. The combined colors of white and 
green cover only about 10% of the park (white is 0.39% and green is 
9.97%). This clearly suggests that increasing use will result in a degradation 
of natural quiet in the GCNP; this is clearly unacceptable. 



9.2.4. Summary of Section 3 Requirements 

Though significant reductions in aircraft sound have occurred for areas of the 
Grand Canyon, and though compliance with SFAR 50-2 has been excellent, 
natural quiet is not yet substantially restored to GCNP. This lack of natural 
quiet affects some visitor groups much more than others, with backcountry 
users and river/oar users more affected and frontcountry visitors less 



Conclusion 9.12: 

There has not been a 
substantial restoration of 
natural quiet in Grand Canyon, 
although the NPS 
acknowledges the value of the 
SFAR and the improvement it 
has brought. 



195 



REPORT TO CONGRESS: Restoration of Natural Quiet 




3) 

U 
<0 

•o 
(0 c 

«-> a 

(0 o 

q m 



u V) 




•q- in 



<U X) 




0) — 

— -a 

XI 3 

- <r 

XI 

d ;* 

<r -q- «- 

CM I 

j* i ^- 

<S S) CSJ 

<- cm ro 



n 

3 

a 
<s 

IS 



196 



9.2 Report on Section 3 Requirements: Grand Canyon Natidfial Park 







3) 




u 




(0 




T3 


a 


C 


*-> 


3 


(0 


O 


Q 


CO 


C 


a 


o 


a 


— 


u. 


*■> 


(ft 


(0 




:> 


0) 


a 


•o 


— 


•«* 


LJ 


n 




+» 


o 


3 


z 


O 



T If) 



1) A 





X) TJ 

a) — 3 
- -o <r 

X) 3 




i- - a x 

TJ CO 
3 tt CD 
<Z V - 
CM 1 
tt 1 T 
CO C9 CVJ 

«- CM tO 





197 



REPORT TO CONGRESS: Restoration of Natural Quiet 



CONCLUSION 9.13: 

If no changes ore made to the 

SFAR, progress to date in the 

restoration of natural quiet will 

be lost. Projections suggest that 

without further improvements, 

the loss of natural quiet will 

accelerate to an unacceptable 

level. 

CONCLUSION 9.14: 

The NPS recommends that SFAR 

50-2 be revised to effect a 

greater restoration of natural 

quiet. 



affected . All studies point to these same conclusions, and the NPS is 
obligated, in pursuit of both its Congressionally mandated and defined 
management responsibilities, to seek a further restoration of natural quiet. 
Most visitors support keeping air tour operations numbers at current levels 
or reducing them. 



9.3 What are the Opportunities for Solutions? 

Overflights that impact natural quiet may be divided into two types: 

■ Flights of very low altitude (altitudes of a few hundred feet or less, 
flown primarily by helicopters) which go well beyond the issue of 
natural quiet and enter areas of personal safety, appropriateness in a 
park setting, concern for effects on wildlife, and so forth. 

■ Flights of somewhat higher altitude^r greater lateral distance from 
the visitor which primarily impact natural quiet or the acoustic/ 
aesthetic character of the setting, but little else. 

It is the latter of these two types which is addressed here. 



9.3.1 Realistic Expectations 

The findings of many different studies all strongly indicate that if aircraft fly 
over a national park where quiet is a resource, there will never be complete 
natural quiet at all times and in all places within the park. Instituting 
"flight-free" zones, such as was done under SFAR 50-2 at Grand Canyon 
National Park, may create some areas where aircraft are not audible, but to 
be effective in restoring natural quiet to large areas, flight-free zones will 
need to be very large — on the order of 20 to 30 miles, in minimum 
dimension. Direcdy below authorized flight corridors no reasonable 
minimum altitude either for tour aircraft or for higher altitude commercial 
jet traffic can completely restore natural quiet. Quieter aircraft may help 
restore natural quiet to greater land areas to the side of the flight corridor, 
but not directly beneath it. Beneath the corridor, quieter aircraft can reduce 
the degree of impact, but not eliminate it. 

Reducing the numbers of overflights or increasing the number of passengers 
per aircraft reduces the frequency of the intrusions, and in turn increases the 
uninterrupted periods of time visitors may experience natural quiet. It is 
likely that very large reductions vyould be required at seriously affected parks 
before visitors within one to two miles of flight corridors would experience 
only infrequent impacts to the natural quiet of the environment. 



198 



9.3 What are the Opportunities for Solutions? 



Moving the locations of flight corridors needs to be carefully analyzed so that 
the noise burden is not simply shifted to another area that is just as valued by 
another segment of the visitor population. Natural quiet may be improved in 
one area of the park, but degraded in another. To the extent that visitors are 
geographically distributed over large areas of the park, gains and losses from 
moved flight corridors must be carefully considered. Commercial interests 
may be economically affected by changes in air corridors, and there may be 
safety and regulatory implications as well. 

9.3.2 Realistic Opportunities 

If the FAA and NPS act cooperatively, there are opportunities for problem 
solving. Where aircraft overflights are over or immediately adjacent to park 
boundaries, management must define where it is important to preserve 
natural quiet and what opportunities they seek to provide park visitors. They 
must also ascertain the critical areas of the park and times of day these 
opportunities can be provided, and work with the affected parties to reach 
compromise on achieving their goals. At a minimum, the affected parties will 
include the FAA, air tour operators, and park management. 

Separation of Visitors and Overflights. Defining certain areas of the 
park for tour overflights is likely to be the first step. In so doing, natural 
quiet under and to the side of corridors will be degraded. The loss of natural 
quiet is the consequence of accommodating aircraft overflights. Mitigation 
opportunities in the land areas adjacent to flight areas or corridors will be 
park specific, and may take advantage of natural attenuation opportunities. 

Exploiting Natural Attenuation. To the extent that altitudes can be 
minimized (without going below reasonable minimums), park terrain can 
sometimes be used to acoustically shield flight-free areas from aircraft noise. 
If hills or ridges are available, lowering aircraft altitudes may be a 
consideration. By lowering altitudes, areas directly beneath flight corridors 
that are already impacted will have impacts intensified, but if local terrain 
features are present, land areas where the protection of natural quiet is 
important may be increased. Breaking the line-of-sight between the visitor 
and aircraft can reduce maximum noise levels by an amount that would 
otherwise be gained only by a near doubling of the distance between aircraft 
and the visitor. 

In flat or open areas where terrain shielding cannot effectively be used, 
distance (either in altitude or laterally) is a mitigation option. Very large 
distance changes may be necessary to achieve natural quiet, however. To a 
first approximation, 10 decibels of reduction can be expected for every 
doubling of distance between the visitor and aircraft at its closest point of 
approach. Thus, to obtain the first 10 decibels of reduction, the existing 
distance between aircraft and the nearest visitor would have to be doubled. 



199 



REPORT TO CONGRESS: Restoration of Natural Quiet 



To obtain 20 decibels of reduction the distance would have to be 
quadrupled, and to obtain 30 decibels of reduction, the distance would have 
to be increased by a factor of eight. 

Encouraging Noise Reduction at the Source. Another mitigation 
measure is encouraging and phasing in quieter aircraft, or retrofitting 
existing aircraft. Aircraft speed, power, and propeller pitch on fixed-wing 
aircraft, and flight regimes which eliminate blade slap for helicopters are also 
effective mitigation measures to be taken at the source of the noise. 
Relationships between these variables and aircraft noise levels will be aircraft 
specific, and may require additional study. The NPS believes that quiet 
aircraft will, over time, contribute to the mandated substantial restoration of 
natural quiet at GCNP. Figure 9. 12 shows a comparison between 
observer-based audibility contours for quieter aircraft (a deHavilland 
DHC-6-300 Twin Otter and the McDonnell Douglas MD-900 NOTAR 
Helicopter) vs. louder aircraft (Cessna 207/402 and a Bell Jet Ranger 
helicopter). This graphic shows clearly the critical need to reduce noise at 
the source. 

Reducing Duration of Noise Intrusions. Limiting times of day may be 
another mitigation alternative, but this measure may result in a greater 
intensity of flying during other portions of the day. This alternative may not 
be met with enthusiasm from air tour operators, however, since their 
investment in aircraft could remain unproductive for periods of time. 

Encouraging Use of Greater Payload Aircraft. Tour aircraft which can 
accept greater numbers of passengers without substantial increases in noise 
level emissions may be an attractive step toward mitigation in some 
circumstances. With larger numbers of people per flight, and fewer flights, 
the percentage of time that natural quiet is compromised would be reduced. 



CONCLUSION 9.15: 

The uniqueness of individual 

park units, their visitation 

areas, and their opportunities 

for mitigation to improve 

natural quiet strongly suggests 

that in a systematic approach 

to problem solving, flexibility 

will be essential to get to 

productive park-level solutions. 



9.3.3 Environment Needed for Effective Comprehensive Solutions 

Some parks have the unique resource of natural quiet to be protected. This 
resource may be concentrated in limited areas of some parks, or distributed 
over large areas of others. Each park also has unique air tour attractions. In 
some parks, these attractions are fixed in location. In others, such as Hawaii 
Volcanoes NP, areas of air tour interest change weekly or even daily. Parks 
also have unique mitigation options which affect how sound propagates from 
aircraft to areas where natural quiet is to be protected. These parks need 
unique airspace management plans approved by the FAA. 



200 





■■■■■■■■ 



1 to 10000 ft 

2 10000 to P0000 

3 ?0000 to 30000 
1 30000 to 40000 



5 40000 to 50000 

6 50000 to 60000 

7 60000 to 70000 

8 70000 to 80000 



9 80000 to 90000 

10 90000 to 100000 

1 1 1 00000 lo 1 1000C 



Figure 9.12: Observer-Based Audibility Contours Comparing Quiet and Other Aircraft 



201 



REPORT TO CONGRESS: Restoration of Natural Quiet 



CONCLUSION 9.16: 

Interagency airspace 

management coordination 

guidelines are needed to 

outline agency responsibilities 

and interfaces on overflight 

issues. 



For -these reasons, effective solutions to restoring the natural quiet in parks 
must be sought at a local level. A national-level framework or process is 
necessary to facilitate this. Tools tor identifying opportunities for 
improvements, and tools tor evaluating the effectiveness of improvements 

must be provided to local park management. They must also be equipped 
with a set of procedures for using these tools that will guide them through 
the process to satisfactory solutions. As part of the 1992 park manager's 
survey, management was asked how strongly they would support a formal set 
of procedures to resolve overflight issues. Over 80 percent of the managers 
indicated a moderate to extreme support for formal procedures. 



9.4 Summary 

Simple limitations on altitude can diminish the impacts of overflights, but it 
is unlikely that those limitations alone will effectively restore natural quiet. 
In the case of Grand Canyon, even SFAR 50-2 could not produce a 
substantial restoration of natural quiet, although its value is recognized. 
Visitors are sensitive to the diminution of natural quiet, and many rate 
experiencing natural quiet as an important reason for visiting the Grand 
Canyon.Visitors to other parks also rate experiencing natural quiet as an 
important part of their visits. 

The failure to substantially restore natural quiet should not be interpreted as 
an indication of the failure of any group to take appropriate action. It is an 
indication of the difficulty of finding solutions that will make the effective 
use of airspace and preserve park resources simultaneously. The NPS 
recommends that SFAR 50-2 be revised by the FAA to contribute to a more 
effective restoration and maintenance of natural quiet over time. 



202 



tffa(& 



10 



CONCLUSIONS AND RECOMMENDATIONS 



The information and analyses provided in the previous chapters lead first to 
general conclusions about the type and extent of impacts produced by 
overflights, and about the values associated with overflights. These general 
conclusions in turn lead to identification of issues that are addressed through 
NPS recommendations to Congress as requested in Public Law 100-91 . 



10.1 Conclusions 

Nature and Scope of Problem: Aircraft overflights can and do produce 
impacts both on visitors and on park resources. These impacts, however, do 
not occur evenly throughout the park system, but occur at some parks to a 
considerably greater extent than at others. This was confirmed by the NPS 
Manager's Survey and the Visitor Survey. Based on the Visitor Survey for the 
National Park System where there was congruence between visitor and 
manager perceptions of problems in 29 of the 39 parks sampled, it is likely 
that there could be as many as 50 to 100 units of the park system where 
overflight problems are likely or certain to exist. (See Chapter 2). NPS 
managers have consistendy identified 30-40 parks as priorities for research 
and problem solving for nearly a decade. Because of the congruence in 
perspective between visitors and managers, also confirmed in part by 
acoustic research, it is possible to conclude that there are significant 
overflight problems that need to be addressed in 1 5-30% of the National 
Park System. 



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REPORT TO CONGRESS: Conclusions ond Recommendations 



Commercial and sightseeing operations are more common than other types 
of overflights. Military and park administrative overflights are the least 
common. Helicopters and low-level jets are more likely to be of concern to 
park managers than other types of aircraft. The nature of effects on parks is 
varied, as described below. Many relate to aerial sightseeing, others to 
low-level military overflights. Some are noise-related, some are visitor 
experience-related, and others are safety-related. 

Effects on Natural Quiet: Natural quiet is an important natural resource 
in units of the National Park System. The indigenous sound levels in national 
parks, are often considerably lower than sound levels commonly experienced 
in most residential areas. In such park areas oflow ambient sound levels, 
even distant aircraft can be easily heard. Complete preservation of natural 
quiet under these circumstances can mean that aircraft must fly several miles 
from the area to be protected. Natural quiet is an increasingly scarce 
resource in America. The NPS needs to protect some of these uniquely quiet 
places. 

Effects on Cultural Resources: Cultural and historical resources, sacred 
sites, and ceremonies can be affected by the sight and sound of overflights. 
The setting, ambiance, feeling or association can be disrupted, and vibrations 
may be induced that can be damaging to structures. If helicopters come too 
close to cliff dwellings, there is a potential for loss of cultural resource 
context and materials (pollen, small artifacts, etc.). Potential for impact 
depends upon the proximity of the aircraft overflight to the resource, the 
frequency of overflight, and, for vibration impacts, the frequency-dependent 
responses of the resource to impinging sound or pressure waves. Resources 
should be examined on a case-by-case basis, but general guidelines suggest 
that historic structures exposed either to sonic booms or to helicopter flight 
at close range may be at risk of weakening or damage and should be 
examined to determine levels of sound-induced vibration. In the absence of 
such detailed information, eliminating sonic booms or keeping helicopters 
distant (probably about 2000 feet vertically and horizontally) should serve to 
protect most structures. 

Effects on Wildlife: In general, wild animals respond to low-altitude 
aircraft overflights, although the manner in which they do so depends on 
life-history characteristics of the species, characteristics of the aircraft, flight 
activities, and a variety of factors such as habitat type and previous exposure 
to aircraft. Of most concern in parks are 1) low-altitude overflights by 
military aircraft, and 2) light, fixed-wing aircraft and helicopter activities 
related to tourism. The primary concern stemming from these low-level 
overflights related to wildlife is that the flights may cause physiological and/or 
behavioral responses that in turn reduce the wildlife's fitness or ability to 
survive. Overflights may cause excessive arousal and alertness or stress. II 



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JO. J Conclusions 



chronic, stress can compromise the general health of animals. Overflights 
may interfere with raising young, habitat use, and physiological energy 
budgets. Indirect effects on wildlife such as accidental injury, energy losses, 
habitat avoidance and abandonment are very difficult to detect, but some 
experts suspect they occur. 

Recent concerns have focused on the significance of overflight impacts as 
they affect wildlife populations. Based on a limited number of studies it can 
be concluded that impacts to wildlife populations can occur from low level 
aircraft overflights. It would be valuable to have additional research to fully 
address population impacts, but waiting for and relying on luture research 
results for current policy decisions is not possible. Criteria are identified in 
this report that the NPS proposes to use to trigger mitigation or prevention 
efforts. 

Effects on Park Visitors: Visitors report impacts (interference with 
enjoyment, annoyance, and interference with appreciation of natural quiet), 
depending upon the levels of overflight sound which the visitors may have 
experienced. However, reported impacts are highly variable from location to 
location, and the results of the dose-response work and the survey of Grand 
Canyon visitors suggest that visitor sensitivity to overflight-produced sound is 
greater for activities where visitors remove themselves from automotive 
transportation and, possibly, from other visitors. Backcountry visitors, people 
on oar-powered river trips, and visitors who take short hikes away from their 
cars, consistendy show greater sensitivity to the sound of overflights than do 
frontcountry visitors, including visitors at easily accessible overlooks. These 
findings lend credence to the need for a systematic approach to problem 
solving of park overflight issues, but one which can target specific problems 
in specific areas. 

Overflights and Safety: Although there is no evidence of serious or wide 
spread safety problems for on-ground visitors or park employees tied to 
aircraft overflights, there are at least 1 8 parks where safety from an 
on-ground perspective needs further investigation and evaluation. Virtually 
no visitors perceived a threat to their safety from overflights. Some 
organizations and individuals in the outdoor recreation community 
expressed concerns, but the overflight incidents triggering these concerns 
may be isolated incidents or reactions to other types of impacts. As in the 
case with other overflight impacts, identifying and correcting safety problems 
should be done on a park-by-park basis. The NPS needs to clearly 
communicate the FAA process by which park managers should identify, 
document and request assistance from the FAA to resolve these issues. 

Airspace over public lands is in demand from many sources — military 
operations, general aviation, air tourism operations, and by land management 
agencies that operate the second largest fleet of aircraft in the country. The 



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REPORT TO CONGRESS: Conclusions and Recommendations 



potential tor conflict, especially during fire fighting or other major incidents, 
is real and growing. The NPS and other land management agencies need to 
work with DOD and FAA to develop procedures that will resolve these 
airspace/park management issues in complex airspace. Improving 
communication links is vital. 

Values Associated with Aircraft Overflights: Aviation helps the NPS 
effectively administer the National Park System, many visitors enjoy the 
experience of seeing parks from a different perspective, and it is a special 
opportunity for the disabled, elderly, and infirm. But given the potential for 
impacts to on-ground visitors and park resources, air tour passenger 
enjoyment adds to the complexity of the situation. Should the NPS consider 
air tour passengers as park visitors since their enjoyment derives from the 
resources that park preserves? Unlike other visitors where the NPS controls 
visitor activity to prevent or minimize degradation of park resources and 
experience opportunities, the impacts of these "visitors" are not controlled 
by the NPS. This situation is a source of great frustration to NPS managers 
that needs to be appreciated by the FAA. It is essential that the FAA and NPS 
find a way to mitigate these impacts. 

The marketability of air tours also adds to the complexity of the situation 
because it suggests continued growth of tours over parks. The willingness of 
vacationers to take air tours, and to endorse that "product" suggests to 
entrepreneurs that there may be opportunities for expanded air tour 
services. This, in turn, suggests that problems may get worse. 

The NPS believes that these "aerial visitors" should be treated as park 
visitors, subject to similar benefits and restrictions as other visitors. (Grand 
Canyon National Park has considered air tour passengers as park visitors 
since 1993). This is only possible if there is a way to feasibly mitigate or 
regulate the effects of these users. 

Overall NPS Conclusion: Aircraft overflights can cause impacts to park 
resources and values. For certain visitors, for visitors engaging in certain 
activities, and for certain areas, there is a very real potential for overflights to 
impact parks' natural and cultural resources, visitor experiences, and solitude 
and tranquillity — the very fabric of many national parks. A systematic 
framework for addressing these problems is a first step; it should be flexible 
enough to address the unique airspace/park use issues identified in this 
report. NPS priorities should be used to effectively focus problem-solving 
efforts. At the same time, aviation confers benefits to the parks and to some 
park visitors. The NPS needs the assistance of FAA and the Department of 
Defense so that the scarce resources of natural quiet and airspace can be 
most effectively conserved for the common good and benefit of the 
American public, while also preserving the benefits provided by aviation. All 
of the involved agencies have very different missions with little tradition for 



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10.2 Airspace Management Issues: The NPS Perspective 



working together for effective solutions. This needs to change, and there is 
some evidence that diis is possible. 

The issue is not whether there is an impact, but rather how much impact 
does there have to be before NPS can be assured of relief. Through this 
report, the NPS has made an important first step at defining how significant 
these impacts can become before they should "trigger" FAA action. The NPS 
recommends that these definitions of impact be accepted as a starting point, 
ones that can be refined over time as research and experience in application 
dictate. 

Aircraft overflights of national parks are variable in number and nature. 
Solutions to airspace/park use issues are likely to be equally diverse. There 
may be solutions or partial solutions to many problems identified in this 
report; however, the NPS recognizes that resolution may not be possible for 
some issues at this time. Getting to solutions dictates that issues be clearly 
identified and addressed by the agencies involved. 



10.2 Airspace Management Issues: 
The NPS Perspective 

Public Law 100-91 studies and investigations conducted by the NPS suggest 
that the following issues should be addressed: 

■ Lack of Airspace/Park Use Issue Resolution Process: The 

majority of issues identified in this report occur at the regulatory 
interface of two Federal agencies. There has been no process or 
systematic basis for dealing with issues on an interagency basis. With 
park resources, including natural quiet and visitor experience, and 
airspace becoming scarce resources, the FAA, NPS, and the military 
services need to develop an airspace/park use issue resolution process 
that respects the authorities and mandates of involved agencies. This 
is a situation where government should be "re-invented". 

The process for identifying problems, developing, testing and 
implementing solutions, and monitoring outcomes should be 
uniform throughout the National Park System. The NPS must have 
the authority to trigger the process for resolution of airspace/park use 
issues. Sufficient experience, information and analytical tools are 
available to assess whether impact reduction methods are effective, 
feasible and verifiable, and whether developing the basic oudines for a 
conflict resolution process is possible. 



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REPORT TO CONGRESS: Conclusions and Recommendations 



■ Aerial Commercial Use of National Parks: The scenic resources 
of national parks are used for commercial purposes by sightseeing 
tours, commercial filming and others. There are commercial air tour 
operations over 30-40 national parks. Several operate under NPS 
concession contracts where the airstrip or airport is inside the park; 
the others do not. Where park resources or visitors are being 
affected by these operations, it is vital that there be a means to 
prevent or minimize impacts. In the same context, the NPS needs 
more effective control over low-level commercial filming over 
national parks. 

■ Inability to Protect Natural Quiet: The NPS believes there 
should be national parks where natural quiet can be preserved and 
experienced by visitors. Both the NPS and the FAA have regulatory 
authorities that can be used to protect natural quiet in national parks, 
but to date these have not been effectively employed for that purpose. 

■ Lack of a Substantial Restoration of Natural Quiet in Grand 
Canyon National Park: SFAR 50-2 has made important progress 
in restoring natural quiet despite a significant increase in air traffic. 
In spite of the best efforts of all involved, the regulation has not 
resulted in a substantial restoration of natural quiet in Grand Canyon 
National Park and the continuing growth in air traffic may diminish 
or negate progress to date. The NPS believes that improvements to 
the SFAR are necessary. 

■ Lack of Methods to Prevent Problems: To date the NPS and 
FAA have not developed the methods to effectively prevent 
airspace/park use conflicts. Communication, training and planning 
need to be greatly improved for skills to be developed in this arena. 
This will be vital as the demand for airspace continues to grow. The 
NPS believes that over time, problem prevention will be more 
effective than problem solving. 

10.2.1 The FAA and The NPS: Learning How to Work Together 

On December 22, 1993, Secretary of Transportation Federico Pena and 
Secretary of the Interior Bruce Babbitt, in an important act of reinventing 
government, committed the FAA and the NPS to learning how to work 
together to resolve airspace/park use issues. In March, 1994, the two 
agencies issued a joint Advance Notice of Proposed Rulemaking (ANPRM) in 
the Federal Register soliciting public ideas on how to reduce adverse effects 
from commercial air sightseeing tours on parks such as the Grand Canyon, 



"Overflights of Units of the National Park System", Federal Register Volume 59, No. 52, Thursday, March 17, 1994. 



208 



10.2 Airspace Management Issues: The NPS Perspective 



Hawaii Volcanoes and others (See Appendix D). Questions were solicited on 
a number of policy and technical questions that will be important to guiding 
the two agencies on how to proceed on this issue. 

1 0.2.2 Military Airspace/Park Use Issues: Prospects for Change 

There are some encouraging signs that the military services may be more 
amenable to resolving airspace/park use issues than has been the case in the 
past. The following provides evidence of this trend: 

■ Long-Range Airspace Planning 

In recognition of the need to improve long-range airspace planning, 
the Air National Guard (ANG) implemented a coordinated airspace 
planning process in the Northwest Mountain FAA Region in 1988. It 
then initiated a regional process in the New England FAA Region in 
1989, primarily at the unit level. To improve the process and ensure 
appropriate levels of planning and coordination and to bring a 
national perspective to unit, local, state, and regional airspace issues, 
the ANG involved its leadership and extended the regional approach 
to the remaining FAA regions so that all ANG activity within the 
United States is covered. 

In April, 1993, the ANG established the national-level ANG Airspace 
Steering Committee. The members of the Committee are the 
chairpersons of the regional committees. Acting as the executive 
agent of the Director of the Air National Guard, the Steering 
Committee is charged with guiding the overall airspace planning and 
management process for the ANG. This process involves: 1) 
identifying, validating and ranking airspace requirements on a 
regional basis; 2) defining and selecting preferred solutions; and 3) 
developing a coordinated implementation plan. 

This planning process provides the ANG a guide for decisions and 
actions and ensures that airspace will be available to meet ANG 
training requirements in the next 5-10 years. The process is evolving 
and relies on the involvement of senior ANG leaders from each state. 
In addition, the FAA, Air Staff, Major Commands, Air Force Reserve, 
Army National Guard, Army, Navy, and Marines are becoming part of 
the process. 

NPS and the other land management agencies, for the first time, have 
clearly defined and centralized points of contact to deal with on 
airspace issues that involve the ANG. To the extent that this approach 
to airspace management is adopted by the Department of Defense as 
a whole, it will facilitate both problem solving and problem avoidance. 



209 



REPORT TO CONGRESS: Conclusions and Recommendations 



i Policies of the Air National Guard and Navy: In 1990 the ANG 
instituted an overflights policy on federally designated wilderness and 
wild and scenic rivers (See Appendix E). The policy requires ANG 
units to plan new airspace in a manner that considers these areas as 
sensitive and to be avoided whenever possible. If avoidance is not 
possible then overflights will occur at 2000 feet above ground level 
or higher. Also the U.S. Navy policy on "noise sensitive areas" such 
as national parks is that these areas shall be avoided when at altitudes 
of less than 3,000 AGL, except when in compliance with an 
approved traffic or approach pattern, visual or instrument route, or 
special use air space. Noise sensitive areas are also to be avoided in 
the development of routes and special use airspace unless the 
3,000-foot criteria can be observed. If adopted by all DOD agencies, 
these types of policies could facilitate problem solving and problem 
avoidance. 

i Formation of the Federal Interagency Airspace/Natural 
Resource Coordination Group and DOD Report to 
Congress: In January, 1994, an ad-hoc group from the Department 
of Defense (U.S. Air Force, U.S. Navy, U.S. Army, U.S. Marine 
Corps, Air National Guard, Air Force Reserve, Army National Guard, 
and other Department of Defense officials), Department of the 
Interior (NPS, Fish and Wildlife Service, Bureau of Land 
Management, and Bureau of Indian Affairs), and from the 
Department of Agriculture (U.S. Forest Service) met and agreed to 
establish the Federal Interagency Airspace/Natural Resource 
Coordination Group as the vehicle for addressing airspace conflicts 
over public lands. In May, 1994, the group agreed to a "Statement of 
Principles for a Partnership for Action to Protect, Restore and 
Maintain the Nation's Airspace and Federally Protected Land 
Resources" (Appendix F) and established five permanent 
subcommittees: 

Operations and Safety 
NEPA Planning and Compliance 
Education and Awareness 
Environmental Effects 
Coordination and Procedures 

As part of this effort, the ANG temporarily placed a liaison officer 
with the U.S. Fish and Wildlife Service (Refuge Division) to explore 
solutions to five aircraft overflight issues in the National Wildlife 
Refuge System. The following examples characterize the types of 
resource impacts and solutions that have been so far addressed: 



210 



10.3 NPS Recommendations to Congress 



• offsetting aircraft by one-half mile avoided disturbance of 
nesting piping plovers, a threatened species, on the Edwin B. 
Forsythe National Wildlife Refuge in New Jersey; 

• shifting flight routes one mile offshore reduced disturbance of 
nesting wood storks, an endangered species, on the Savannah 
Coastal Refuge Complex in Georgia; 

• enforcing a 2, 000-foot altitude restriction above Cross Creeks 
National Wildlife Refuge in Tennessee eliminated disturbance 
of nesting bald eagles; 

• eliminating the dropping of flares below 2,000-feet elevation 
eliminated the potential for wildfire and associated impacts to 
endangered species on the Buenos Aires National Wildlife 
Refuge in Arizona; and 

• establishing operational safety protocols on the Charles M. 
Russell National Wildlife Refuge in Montana to reduce the 
potential for airspace conflicts. 

In addition, military and Fish and Wildlife Service representatives 
identified field-level contacts to facilitate implementation of 
agreements and to address additional problems as they occur. The 
solutions are being monitored to ascertain how to ensure that these 
processes are permanendy established. All parties understand that 
good communication is critical to sustain these agreements. 

In a response to the Senate Armed Services Committee Report on 
the National Defense Authorization Act for Fiscal Year 1 994, Report 
No. 103-1 12, the Department of Defense reported that the 
coordinating group may be an important vehicle for establishing 
procedures and dispute resolution mechanisms between the 
Department of Defense and the Department of the Interior. (See 
Appendix G). The Department of Defense has committed to 
reporting to the Senate Armed Services Committee by January 1 , 
1995 on airspace resolution procedures and recommendations 
developed by this ad-hoc coordinating group. 



211 



REPORT TO CONGRESS: Conclusions and Recommendations 



10.3 NPS Recommendations to Congress 

10.3.1 RECOMMENDATION I 

Develop Airspace/Park Use Issue Resolution Processes 

The NPS recommends that the Department of Transportation— Department 
of the Interior Interagency Working Group be maintained as a functioning 
entity to manage interagency problem solving through to the operational 
level of both agencies. Their priorities should be to identify and document 
processes that can be clearly communicated to field offices where problem 
solving should occur. Although many of the recommendations that follow are 
tied to this process, there may be some airspace/park use issues that go 
beyond the scope of the following recommendations. The general shape of 
this process should be as follows: 

■ Define and report issues in a formafagreed upon by the agencies, 
including definitions of impacts oudined in this report. 

■ Forward information to points of contact in NPS and FAA who 
would be expected to seek resolution of the issues. 

■ Specify the time period during which a resolution must be achieved. 

■ Issue a joint report to the Interagency Working Group on success of 
resolution or mitigation efforts. If resolution is not possible, the 
issues would be addressed by the policy group. 

■ Issues not resolvable by the Interagency Working Group would be 
forwarded to the Secretaries of Transportation and Interior for final 
resolution. 

The NPS also recommends that NPS and DOD use the newly established 
Federal Interagency Airspace/Natural Resources Coordination Group (See 
Section 10.3.2 and Appendix F) to develop similar issue resolution processes 
for low-level military overflights. 

10.3.2 RECOMMENDATION 2 

Establish and Maintain Agency Points of Contact 

The NPS strongly recommends that agency points of contact be officially 
established and maintained as follows: 

NPS: Deputy Director and Overflight Studies Coordinator 

FAA: Air Traffic Operations (AAT), Flight Standards (AFS), and 
Environment and Energy (AEE). 



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10.3 NPS Recommendations to Congress 



DOD: To be requested through the new Federal Interagency Airspace/ 
Natural Resources Coordination Group. 

10.3.3 RECOMMENDATION 3 

Use the Full Range of Methods and Tools for Problem Solving 

The NPS recommends that all reasonable methods and tools be used in 
airspace/park use issue resolution processes. The following is a partial list of 
methods, any of which might be reasonably effective, feasible, and verifiable 
for use on a specific situation. The NPS has developed tools that permit 
identification of locations impacted by overflights, that compute, in terms of 
sound levels, the effects of changes in aircraft operations and that can be 
used to measure the reductions in impacts that result from such changes. 
The tools are based on a number of studies including, dose-response results, 
simplified sound level measurement techniques and computer programs that 
estimate sound exposure results from aircraft overflights. 

The partial list of methods includes the following: 

Voluntary Agreements: Voluntary agreements can have a role in 
resolving or mitigating airspace/park use issues if some fundamental 
weaknesses can be addressed. The FAA, the NPS, and air tour operators 
need reasons to enter into these agreements. Furthermore, there are no 
enforcement or penalties involved should operators withdraw from or 
refuse to participate in agreements. If rulemaking or penalties would 
result when voluntary agreements did not work, then all parties would 
have incentives to make and comply with these agreements. 

Incentives to Encourage Use of Quiet Aircraft: NPS research 
suggests that quieter aircraft can play an important role in substantially 
restoring or maintaining natural quiet in parks. Although there is no 
Federal requirement for air tour types of aircraft to be manufactured to 
produce less noise than Stage 3 standards for large commercial aircraft, 
some aircraft are significandy quieter than others and more appropriate 
for use in air tour operations. Because of the significant expense, 
incentives need to be developed to encourage air tour operators to 
replace equipment with quieter aircraft. Internally, the NPS will need to 
work with the Department of the Interior's Office of Aircraft Services to 
also provide incentives for parks to use quiet aircraft. P.L. 102-581, an 
"Act to amend the Airport and Airway Improvement Act of 1982 to 
authorize appropriations, and for other purposes," requires the FAA to 
identify' "any measures to encourage or require the use of quiet aircraft 
technology by commercial air tour operators." The NPS defers to FAA 



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REPORT TO CONGRESS: Conclusions and Recommendations 



expertise on this subject, but strongly recommends that FAA facilitate 
the introduction of quiet aircraft technology to benefit national parks, 
among many others. 

Spatial Zoning: Flight- free zones and flight corridors have been 
implemented in the Grand Canyon with some success. Experience has 
shown that, to preserve or restore natural quiet, flight-free zones must 
be quite large in extremely quiet places, approximately 20-30 miles 
minimum dimension. The problem, discussed in Chapter 3, is that 
some park environments are so quiet that the sound of aircraft can be 
heard at great distances from flight paths. 

Altitude Restrictions: Minimum altitudes can help, but for tour 
aircraft or low-altitude military training, the altitudes necessary to 
significandy reduce impacts may essentially defeat the purpose of the 
overflight. On the other hand, altitude restrictions used in Yosemite and 
Haleakala have helped to reduce the m»st egregious impacts even 
though overflight impacts have not been eliminated. 

Operating Specifications for Operators: As part of its certification 
processes, FAA may require operators to conform with certain 
operational requirements. These requirements generally identify the 
types of operations authorized, the types of airplanes permitted, airports 
authorized for use and time limitations for maintenance, and training. 
Operations specifications that relate direcdy to park overflight 
operations may provide a reasonable method to address some 
documented adverse effects of overflights. 

Treatment of Air Tour Operations as Concessions: National parks 
treat all commercial services provided to visitors in parks as concessions 
(i.e. regulated industries) which insures services will conform to 
minimum standards, are not priced unreasonably, and are consistent 
with park values. In some ways, air tour operations are similar to 
ground-based services. In fact, where airstrips are inside parks, the NPS 
has several air tour operations under concession permit. If a joint 
FAA-NPS permitting process can be developed, similar arrangements 
may be possible where it is determined that air tour operations use the 
resources of the national parks. The purpose of this is to reduce 
resource impacts and to provide a specific visitor service. 

Noise Budgets: Noise budgets have been used at some airports 
(Denver-Stapleton was one of the first) to allot responsibility for and 
control of noise among operators. Such budgets assume that the total 



2 . The FAA is awaiting completion of the NPS Report to Congress before it completes the report required by the Airport and Airway Safety, Noise 
Improvement, and Intermodal Transportation Act of I 992. 



214 



JO. 3 NPS Recommendations to Congress 



noise generated by the airport, and by each operator, can be quantified. 
Each operator can be allocated an amount of "noise," generally based on 
an existing or previous level of operations. If an operator uses quieter 
aircraft, through retrofit or new purchases, more flights can be 
conducted while staying within the budget. Budgets are negotiated 
rather than imposed. Noise budgets may provide a means for limiting 
growth in air tour traffic over parks in that they focus on the goal of 
limiting or reducing the impact of the sound of overflights, not on 
direcdy limiting the number or type of aircraft operations. A draw-back 
for park application may be the need for tracking numbers of operations 
by time and type of aircraft. Another drawback is that adverse effects to 
visitor experience may not necessarily be addressed. 

Limits on Times of Operations Some sensitive areas on the ground 
may have cyclical daily, weekly or seasonal high and low visitation 
periods. Aircraft operations may be timed to coincide with low use 
periods. Alternatively, air tours may have slow days, periods or seasons, 
and visitors in search of tranquillity and natural quiet could be informed 
of the best times to visit the park and avoid significant numbers of 
overflights. Limited "No Fly" periods could provide visitors with 
certainty of natural quiet in some parks and should be further evaluated. 

10.3.4 RECOMMENDATION 4 

FAA to Address High Priority NPS Airspace/Park Use Issues 

The NPS recommends that NPS/FAA/DOD joindy commit to resolving and 
mitigating airspace/park use issues beginning with identified priority areas. 
Such a commitment may enable the agencies to develop and more effectively 
communicate how issues can be resolved at the local level. 

v 

10.3.4. 1 NPS Managerial Priorities 

NPS believes its managers' identification of areas with aircraft overflight 
problems is a relatively accurate indicator of where airspace/park use issues 
exist. There is basic congruence between manager and visitor perceptions. 
Many of the 98 areas identified by managers have some type of 
overflight-related problem. Mitigation is possible for some areas and unlikely 
for others. The NPS seeks resolution of its top priorities and recognizes that 
the others (See Appendix B) merit further investigation as well. Based on top 
priority NPS areas for resolution of airspace issues include: 

Grand Canyon National Park 
Hawaii Volcanoes National Park 
Haleakala National Park 
Greaf Smoky Mountains National Park 



215 



REPORT TO CONGRESS: Conclusions and Recommendations 



Glacier National Park 
Bryce Canyon National Park 
Bandelier National Monument 
Statue of Liberty National Monument 

The NPS will further evaluate the complex air traffic patterns over Yosemite 
National Park and Cumberland Island National Seashore to see if mitigation 
appears to be possible and will then discuss those situations with FAA. 

10.3.4.2 NPS Priorities for Protection of Natural Quiet 

The following is a list of parks where the NPS believes maintaining or 
restoring natural quiet is an immediate priority. Natural quiet is an 
increasingly scarce resource in the United States. There ought to be national 
parks where this can be experienced. Criteria for the selection of these areas 
is listed in section 10.3.6. Highest priority areas meeting these criteria 
include: 

m 

Glacier National Park 

Zion National Park 

Southeast Utah Group Parks 

Haleakala National Park 

Crater Lake National Park 

Isle Royale National Park 

Mesa Verde National Park 

Rocky Mountain National Park 

Chaco Cultural National Historical Park 

The NPS will work with the FAA to further refine the criteria and how they 
may apply to other parks. 

10.3.4.3 NPS Priorities for Resolution of Safety Concerns 

The NPS recommends that its perceived on-ground safety concerns related 
to overflights be investigated by FAA to see if these problems can be resolved 
or mitigated. The FAA and the NPS are cooperating in an effort to identify 
and put into effect recommended air tour patterns and altitudes that will 
enhance aviation safety around the Statue of Liberty and reduce other 
impacts there as well. Additionally, the FAA is developing a Special Federal 
Aviation Regulation that will improve the safety of commercial air tour 
operations in Hawaii. The priorities for the NPS include: 

Statue of Liberty National Monument 

Hawaii Volcanoes National Park 

Perry's Victory Memorial & International Peace Park 

The process exists for the FAA to use its authority and expertise to resolve 
reported safety issues. These and any other issues that are identified by park 
managers will be forwarded to the FAA for investigation and resolution 
through the FAA's compliance and enforcement program. 



216 



10.3 NPS Recommendations to Congress 



10.3.4.4 NPS Priorities for Problem Solving with Department of 
Defense 

The NPS recommends that NPS and DOD agencies explore resolution of 
airspace issues at the following priority areas through the Federal Interagency 
Airspace/Natural Resources Coordination Group. It will be important for the 
FAA to be involved in this process as well. This group will report to their 
respective policy representatives by the end of 1 994 on recommendations 
for resolving existing and potential airspace conflicts. NPS priorities for areas 
to be examined during this search for procedures include the following: 

Congaree Swamp National Monument 
Sequoia-Kings Canyon National Parks 
Organ Pipe Cactus National Park 
Death Valley National Park 
Channel Islands National Park 
Joshua Tree National Park 
Petrified Forest National Park 
Pu'ukohola Heiau National Historic Site 
Gulf Islands National Seashore 

Everglades National Park/Big Cypress National Preserve/ 
Dry Tortugas National Park 

DOD is required to report back to the Senate Armed Services Committee on 
development of procedures to resolve airspace/park use issues by January 1 , 
1995. The NPS will also report to the Subcommittee on National Parks, 
Forests, and Public Lands as well as to the House and Senate Armed Services 
Committees on the success and utility of this approach to problem solving. 

10.3.5 RECOMMENDATION 5 

Develop an FAA Operational Rule Triggered by NPS 

The NPS recommends that FAA develop an operational rule to regulate air 
tour operations where they have or may have adverse effects on national 
parks. If voluntary agreements are not adequate, the NPS should be able to 
trigger action by the FAA to delineate aerial sightseeing areas defined by FAA 
Handbook 92.01 for Principal Operations Inspectors, entided Air Tour 
Sightseeing Operations. The NPS would forward recommendation on the 
size, altitudes and routes to effect noise abatement and mitigate impacts to 
persons and property on the ground in parks. The FAA may adjust the 
recommendations and incorporate them into tour operators' operation 
manuals. The rule would need to specify that tour operators operate in 
accordance with Part 1 35 FAA Regulations. Any request by an operator to 
the FAA to fly below 2,000 feet or within 2,000 feet horizontally of sensitive 
areas and structures would need clearance from the FAA only after 
coordination and concurrence by the park manager. 



217 



REPORT TO CONGRESS: Conclusions and Recommendations 



This rule would minimize the effect on other types of aviation by targeting 
specific problem areas. The rule's existence would facilitate the use of 
voluntary agreements. The NPS recommends FAA consider a special 
sub-part of 1 35 regulations to be developed for air tour operations. 

Areas where this rule is most needed include the national parks in Hawaii, 
Glacier National Park, Canyonlands National Park, Great Smoky Mountains 
National Park, Zion National Park, Bryce Canyon National Park, and Rocky 
Mountain National Park. 

10.3.6 RECOMMENDATION 6 

Develop an FAA Rule to Facilitate Preservation of Natural Quiet 

The NPS recommends that FAA, under the authority of Section 6 1 1 of the 
Federal Aviation Act, implement a rule which would provide for the 
protection of natural quiet. 

Several nationally applicable environmental statutes and regulations recognize 
that there are circumstances where special protection — beyond ordinary 
performance standards or requirements — may be necessary to adequately 
protect nationally significant resource values. 

Class I Designations under the Clean Air Act require new air pollution 
sources which may affect designated airsheds — including many in national 
parks — to prevent significant deterioration of existing air quality so that 
resources including air quality- related values such as scenic vistas are not 
adversely affected. The absence of air pollution in some areas is what makes 
us aware of air pollution in others; if all areas are equally polluted, we have 
no way to know what is natural. Most Class I areas are at least 5,000 acres in 
size. 

Outstanding National Resource Waters (ONRW) designations under 
the Clean Water Act often mean that no new point source discharges of 
pollutants are permitted in streams or other water bodies designated as 
ONRW. Waters in national parks are specifically referred to in the regulation 
that implements ONRW and several states have designated ONRW in parks. 
Their overall purpose is to keep the cleanest of the nation's waters clean. 

The provisions of Section 522, Designating Lands Unsuitable for all or 
certain types of mining, of the Surface Mining Reclamation and Control Act, 
allow for the protection of unique resources, such as those in the National 
Park System, by prohibiting all or certain types of coal mining in certain 
areas. In one such designation, the Secretary of the Interior found some 



3. 49 U.S.C. Section 44715. See also 49 U.S.C. 303 (a) and (c). 



218 



10.3 NPS Recommendations to Congress 



federal lands adjacent to Bryce Canyon National Park to be unsuitable for 
surface mining because of the potential for adverse effects to scenic resources 
and quiet. 

Each process shows that what is generally applicable may not adequately 
safeguard the unique resources and attributes of special, nationally significant 
lands and that as a consequence, designations or categories need to be 
implemented that establish a higher standard of protection. The NPS 
believes that there are parallels between these processes and 
overflight- related adverse impacts to units of the National Park System. 
Practices that are generally suitable for aircraft elsewhere may not be suitable 
in a limited number of cases where natural quiet or especially sensitive 
cultural resources or threatened or endangered species can be adversely 
affected by overflights. The NPS believes the following criteria can provide a 
starting point for establishing a similar process for outstanding natural quiet 
parks: 

■ Critical habitat for an endangered species known to be adversely 
affected by noise (e.g., the grizzly bear in the lower 48 states). 
Excessive and avoidable noise could be found to be an adverse 
modification of habitat. 

■ Seriousness and solemnity of purpose characterizes the park unit or a 
portion thereof and the sights and sounds of overflights can diminish 
the ability of visitors to experience — with respect and reverence — 
the resources and values embodied in selected Civil War battlefields 
or Mount Rushmore, for example. 

■ Natural quiet is a central resource value to the park and its absence 
imperils the totality of the visitor experience, especially when the 
visitor comes to the park expecting peace and quiet and enjoyment 
of nature and natural sounds. For example, an experience in a 
canyon in southern Utah is not complete without the call of a canyon 
wren or the sounds of wind. An experience of the northern lakes is 
not complete without the call of loons. 

■ Wilderness has been designated on all or part of the park, and given 
characteristics of the terrain and sound attenuation, opportunities for 
solitude would be substantially diminished by overflights. This 
requires the area to be at least 5,000 acres in size unless there are 
special circumstances. 

In some cases these criteria could be used as the basis to petition the FAA to 
implement, through their rulemaking process, an aircraft management plan 
for that park to establish flight corridors or flight tracks that would keep 
areas naturally quiet and preserve the visitor experience of them. 



219 



REPORT TO CONGRESS: Conclusions and Recommendations 



10.3.7 RECOMMENDATION 7 

Develop a Movie Waiver Policy 

The NPS recommends that FAA amend its policy relating to the conditions 
and limitations for movie filming operations conducted in national parks. 
The new policy should require the operator flying the filming crew to have 
the following: 

■ An operating plan specific to the park where the filming is being 
done. 

■ Approval of the plan by the park superintendent 

■ Notification of the appropriate Flight Standards District Office 
(FSDO) 

10.3.8 RECOMMENDATION 8 

Develop an Interagency Airspace Coordination Guide/Training 

The NPS recommends that the NPS, FAA, and the military services complete 
an Interagency Airspace Coordination Guide that would incorporate what 
the agencies learn about how to resolve airspace/park use conflicts. The NPS 
and the Air National Guard are currendy developing a proposal to DOD's 
Legacy Program for that purpose. It is further recommended that this be the 
basis for training interagency planners from all the agencies involved, pilots 
from the Armed Services, etc. 

10.3.9 RECOMMENDATION 9 

Seek Continued Improvements in Safety and Interagency Planning 
Related to Airspace Management 

The NPS makes the following recommendations with respect to safety and 
planning: 

■ FAA and NPS work together joindy to investigate the parks where 
serious safety issues may exist. FAA would take corrective actions if 
appropriate. 

■ FAA and NPS joindy develop a reporting format for safety issues to 
be used as part of interagency issue resolution processes. The NPS 
would use this format to report additional issues as they arise. 

■ Land management agencies, the FAA and the DOD need to give 
greater priority to identifying how to avoid collisions associated with 
the Temporary Flight Restrictions around forest fires. Department of 



220 



J0.3 NPS Recommendations to Congress 



the Interior agencies need to support development and use of 
CAHIS (Computer-Aided Hazard Information System). 

■ Land management agencies, including the NPS, should provide the 
Armed Services with geographically-based databases of their noise 
sensitive areas for use in Armed Services planning. 

■ All the agencies need to explore how to get critical items highlighted 
in each others' planning processes. 

10.3.10 RECOMMENDATION 10 

Improve SFAR 50-2 to Effect and Maintain the Substantial 
Restoration of Natural Quiet at Grand Canyon National Park 

Section 3(b)(3) of P.L. 100-91 requires the NPS to discuss: 

. . . such other matters, including possible revisions in [Special 
Federal Aviation Regulation 50-2], as may be of interest. 

In Chapter 9, the NPS concluded that natural quiet in Grand Canyon 
National Park (GCNP) had not been substantially restored and 
recommended SFAR 50-2 be revised to effect a more substantial restoration. 
The following sections propose revisions to Special Federal Aviation 
Regulation 50-2 for the purpose of not only achieving substantial 
restoration of natural quiet but also for maintaining that restoration over 
time, as increases in the air tour industry occur. If the FAA determines that 
there are no safety concerns , these revisions can be introduced into the FAA 
rulemaking process where they would undergo analysis, public review and 
comment. The NPS is supportive of anything the FAA can do to lessen the 
regulatory burden of the SFAR. 

Aircraft overflight activity at GCNP can be viewed as consisting of the 
following major elements: 

■ The structure of the GCNP Special Flight Rules Area (established by 
SFAR 50-2 in 1988), including the regulation boundary, flight-free 
zones, air tour routes, general aviation and air tour minimum sector 
altitudes, etc. 

■ Aircraft equipment used in the Special Flight Rules Area (SFRA). 

■ Aircraft operations (numbers of aircraft, times of day, etc.) in the 
SFRA. 

■ Aircraft flying above or adjacent to the SFRA. 



Section 3(b)(2) of P.L. 100-9 1 requires the FAA to review NPS recommendations to determine whether implementing them would adversely affect 
aviation safety. 



221 



REPORT TO CONGRESS: Conclusions ond Recommendations 



This recommendation is organized by the same categories and is based on 
the following general concepts: simplification of the commercial tour route 
structure; expansion of flight-free zones; accommodation of the forecast 
growth in the air tour industry; phased in use of quiet aircraft technology; 
and institution of changes in approaches to park management. 

One of the key changes in park management will be the establishment of an 
acoustic monitoring program by the NPS in coordination with the FAA. The 
NPS will replace its current monitoring program with one designed to 
measure sound levels on the ground where the agency seeks to protect 
natural quiet. The NPS will identify benchmark sites and establish a protocol 
for collecting acoustical data at those sites for the purpose of establishing 
"action triggers" (described in section 10.3.10.3). The "trigger" will specify 
a noise level that should not be exceeded. The consequences proposed for 
exceeding the trigger are also described in Section 10.3.10.3. 

10.3.10. 1 GCNP Airspace Structure Recommendations 

The proposed airspace structure, including flight-free zones and flight 
corridors, recommended to effect a more substantial restoration of natural 
quiet for GCNP is displayed in Figure 10.1. 

General 

The NPS recommends that: 

■ The SFRA boundary be modified near the southeast corner of the 
Bright Angel Flight-Free Zone and the far western edge of the SFRA 
near the Grand Wash Cliffs. The purpose of these boundary 
adjustments is to ensure that almost all of GCNP lies within the 
SFRA. The FAA may have to modify the boundary elsewhere to 
guarantee that all commercial aircraft remain within the SFRA while 
conducting tours. The NPS also recommends that the SFRA 
boundary be realigned as originally proposed by NPS in 1987 near 
the Grand Canyon West Airport. A "notch" was cut out of the SFRA 
to accommodate this airport when it was constructed. The NPS 
recommends that traffic utilizing the Grand Canyon West Airport 
have the same caveat ("Landing/Take-off operations below 3,000' 
AGL within 3 NM of the airport are authorized by the SFAR") as 
other airports/airstrips located under or adjacent to the SFRA (e.g., 
Marble Canyon Airport, Cliff Dwellers Airstrip, Grand Canyon Bar 
Ten Airstrip, and Pearce Ferry Airstrip). 



222 



10.3 NPS Recommendations to Congress 



■ It is additionally recommended that FAA study the air traffic in the 
range of 14,499 feet Mean Sea Level (MSL) to 17,999 feet MSL so 
that a determination can be made as to whether there is merit in an 
upward adjustment of the SFRA ceiling. 

■ "Minimum Altitude Sector" boundaries (tor the five sectors within 
the GCNP SFRA) remain unchanged. The minimum altitudes within 
these boundaries are proposed to remain unchanged for general 
aviation aircraft, but will change for air tour aircraft as specified 
under "Routes" below. 

■ A new regulation superseding SFAR 50-2 should be considered a 
permanent Federal Aviation Regulation without an expiration date. 

Flight-Free Zones 

The NPS recommends that: 

■ Flight-free zones be expanded to reduce impacts to natural quiet, 
while still providing viable opportunities for air tours. Figure 10.1 
provides a general description of the recommended modifications. 
The NPS will work with the FAA to develop the legal descriptions of 
the four flight-free zones. The current Bright Angel and Shinumo 
Flight-Free Zones would be combined and increased in area to the 
north (to the SFRA boundary); the current Desert View Flight-Free 
Zone would be expanded to the north and south (and to the east to 
the SFRA boundary); and the current Toroweap/Thunder River 
Flight- Free Zone would be expanded to the west and south (and to 
the north to the SFRA boundary). A new flight-free area, the Sanup 
Flight-Free Zone, would be created in western Grand Canyon. 
Flight-free zone boundaries are recommended to extend, in some 
cases, beyond the boundary of GCNP, to provide additional 
protection. 

■ The resulting four (4) flight-free zones be identified as follows (from 
east to west): Desert View, Bright Angel, Toroweap/Thunder River, 
and Sanup. These four zones would encompass approximately 
987,200 acres or almost 82 percent of the total park area. 

■ FAA study air traffic over the flight-free zones in the range of 14,499 
MSL to 17,999 MSL to evaluate the merit of raising the flight-free 
zone ceilings for the purpose of reducing the numbers of aircraft 
flying direcdy over flight-free zones, as well as reducing noise levels 
of those aircraft. 



223 



REPORT TO CONGRESS: Conclusions and Recommendations 



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224 



10.3 NPS Recommendations to Congress 



Flight Corridors 

The NPS recommends that: 

■ Dragon Flight Corridor. On the effective date of a new regulation 
superseding SFAR 50-2, the Dragon Flight Corridor would be 
abolished. However, the Black 1 Alpha (airplane) and Green 1 Alpha 
(helicopter) commercial tour routes (as designated under SFAR 
50-2) would remain accessible for use by quiet commercial aircraft 
only (see the Aircraft Equipment Recommendation section below). 
These routes would be provided to offer an incentive for air tour 
companies to convert to quiet aircraft, and to reward those 
companies which have already converted. The routes are indicated by 
a dashed line in the center of the new Bright Angel Flight- Free Zone 
(Figure 10. 1), and would be modified slightly to avoid overflying the 
Hermit Basin region. Five years after the effective date of the new 
regulation, these two quiet-aircraft routes would be eliminated. 
During the five-year period, traffic along these quiet-aircraft routes 
would be one-way only. Minimum altitudes along these routes would 
remain unchanged. General aviation aircraft, like non-quiet 
commercial tour aircraft, would no longer have access to the Dragon 
Flight Corridor since it would have ceased to exist. 

■ Fossil Canyon Flight Corridor. Five years after the effective date 
of a new regulation superseding SFAR 50-2, for commercial aircraft, 
the commercial tour routes within the Fossil Canyon Flight Corridor 
would be accessible only to quiet commercial aircraft (see section on 
Aircraft Equipment Recommendations). Minimum altitudes within 
this corridor for commercial tour and general aviation aircraft would 
remain the same. Effective immediately upon implementation of the 
new regulation, the dimensions of the corridor would be changed to 
conform with the structure of the Zuni Point Flight Corridor (i.e., 2 
nautical miles wide for commercial tour and 4 nautical miles wide 
for general aviation aircraft). As with the Zuni Point Flight Corridor, 
the general aviation portion of the corridor would be centered 
direcdy over the commercial tour portion. Two-way traffic within 
the Fossil Canyon Flight Corridor by commercial tour aircraft would 
be prohibited. Two-way traffic within the Fossil Canyon Flight 
Corridor by general aviation aircraft would be permitted. Use of the 
Fossil Canyon Flight Corridor by quiet commercial tour and general 
aviation aircraft would continue unless results from the NPS acoustic 
monitoring program indicate a need for change (i.e., action triggers 
were met or exceeded). 



225 



REPORT TO CONGRESS: Conclusions ond Recommendotions 



■ Zuni Point Flight Corridor. Ten years after the effective date of a 
new regulation superseding SFAR 50-2, for commercial aircraft, the 
commercial tour routes within the Zuni Point Flight Corridor would 
be accessible only to quiet commercial aircraft (see section on 
Aircraft Equipment Recommendations). Minimum altitudes within 
this corridor for commercial tour and general aviation aircraft would 
remain the same. The dimensions of the corridor (2 nautical miles 
wide for commercial tour and 4 nautical miles wide for general 
aviation aircraft) would remain unchanged. Two-way traffic within 
the Zuni Point Flight Corridor by commercial tour aircraft would be 
prohibited. Two-way traffic within the Zuni Point Flight Corridor by 
general aviation aircraft would be permitted. Use of the Zuni Point 
Flight Corridor by quiet commercial tour and general aviation 
aircraft would continue unless results from the NPS acoustic 
monitoring program indicate a need for change (i.e., action triggers 
were met or exceeded). - 

■ Tuckup Flight Corridor. The Tuckup Flight Corridor would 
continue to be accessible only to general aviation aircraft. The 
alignment and dimensions of the corridor (4 nautical miles wide) 
would remain unchanged. However, the minimum altitude would be 
lowered from 10,500 feet MSL to 9,500 feet MSL. This altitude 
more closely approximates the minimum sector altitude (9,000 feet 
MSL) for general aviation aircraft in this area of the SFRA. Two-way 
traffic within the Tuckup Flight Corridor by general aviation aircraft 
would be permitted. General aviation use of the Tuckup Canyon 
Flight Corridor would continue unless results from the NPS acoustic 
monitoring programs indicate a need for change (i.e., action triggers 
were met or exceeded). 

GCNP SFRA 

The NPS recommends that: 

■ Fifteen years after the effective date of the new regulation 
superseding SFAR 50-2, commercial tour routes within the GCNP 
SFRA would be accessible only to quiet commercial aircraft (see the 
Aircraft Equipment Recommendation section below). That is, 
non-quiet commercial tour aircraft (including NPS aircraft) would 
have their access phased out. Access by general aviation and military 
aircraft would continue unless results from the NPS acoustic 
monitoring programs indicate a need for change (i.e., action triggers 
were met or exceeded). 



226 



10.3 NPS Recommendations to Congress 



Routes 

The NPS recommends that: 

■ Routes and route segments available to the Grand Canyon air tour 
industry under SFAR 50-2 be simplified and reduced, with 
modifications to some of the remaining routes (see Figure 1 0. 1). 

■ One-way traffic on commercial tour routes outside of flight corridors 
be instituted as much as possible. As discussed earlier, two-way 
traffic within flight corridors by commercial tour aircraft would be 
prohibited. 

■ Whitmore Canyon/Wash helicopter routes be treated the same as all 
other commercial tour routes within the GCNP SFRA (i.e., 
numbered, described, etc.), and procedures be identified in the 
FAA's and operators' Operations Specifications manuals. Noise 
abatement procedures would be instituted by the FAA after 
consultation with the NPS. 

■ In addition to the areas, routes and corridors within the SFRA 
limited to quiet aircraft (described under "Airspace Structure 
Recommendations"), quiet aircraft would be allowed to fly at lower 
altitudes than non-quiet aircraft where feasible (see section 

10.3. 10.2). That is, where the option exists, only quiet aircraft would 
be allowed to fly at the minimum altitudes specified for tour aircraft 
in SFAR 50-2. This may require FAA to adjust commercial tour 
route altitudes for non-quiet aircraft upward to meet necessary 
separation standards. This recommendation can be phased in over a 
short period of time (not to exceed 2 years) or instituted 
immediately if there are sufficient quiet aircraft already in service to 
make this recommendation viable while also ensuring that there are 
no adverse impacts to aviation safety. 

■ Tour flight route altitudes be adjusted to prohibit flight below the 
elevation of any canyon rim or feature within one mile (horizontally) 
of the route. Section 3(b)(1) of P.L. 100-91 states that "the 
recommendations shall contain provisions prohibiting thejlight of aircraft 
below the rim of the Canyon.... " The purpose of this recommendation is 
to prohibit flights below the rim of the Grand Canyon, and to ensure 
certain minimum altitudes when aircraft are accessing the Canyon, as 
between the GCNP Airport and the Zuni Point Flight Corridor, or 
when flying across the North Rim. 



227 



REPORT TO CONGRESS: Conclusions ond Recommendations 



10.3.10.2 Aircraft Equipment Recommendations 

NPS recommends that: 

■ FAA and NPS work cooperatively to develop a noise-based definition 
of "quiet aircraft" and identify the list of fixed-wing and rotorcraft 
(current technology) that would qualify for use in the Special Flight 
Rules Area. Existing FAA methodology for measuring aircraft sound 
levels for aircraft, contained in Tide 14 of the Code of Federal 
Regulations, Part 36 (Noise Standards: Aircraft Type and 
Airworthiness Certification, including all subparts and appendices), 
may be applicable to developing this definition. NPS would expect 
that the quietest aircraft currendy operating in the SFRA would 
qualify — the deHavilland DHC-6-300 Twin Otter ("Vistaliner" 
version), the Cessna 208 Caravan, as well as the McDonnell Douglas 
"No Tail Rotor" (NOTAR) helicopters and other quiet aircraft 
which would qualify to operate there. The definition should also be 
such that retrofitted aircraft are able to be added to the "quiet 
aircraft" category. This cooperative effort between the FAA and the 
NPS coincides with the spirit of the amendment to the National 
Environmental Technologies Act introduced by Senator John 
McCain (AZ) and recendy passed by Congress. 

■ The development and implementation of incentives related to quiet 
aircraft be an important component of any proposed changes to the 
SFAR. Incentives would provide a positive balance to added 
restrictions such as increasing the size of flight-free zones or 
removing specific routes. Other incentives for the use of quiet 
aircraft besides allowing the use of "quiet aircraft only" corridors 
would need to be investigated and instituted to encourage companies 
to move forward in converting their fleet as soon as possible. A wide 
array of inducements or incentives may be possible; the FAA should 
appropriately comment on this. The NPS is supportive of making 
incentives available for this purpose. 

10.3.10.3 Aircraft Operations Recommendations 

Based on NPS experience in GCNP, it is apparent that a new regulation 
must also incorporate some form of use limits to accomplish a substantial 
restoration of natural quiet. It is very likely that part of the gain in noise 
abatement accomplished by SFAR 50-2 has been invalidated by the 
continuing increases in aircraft operations. The NPS has every reason to 
believe that this trend will continue. 



228 



J0.3 NPS Recommendations to Congress 



Consequently, to ensure maintaining the substantial restoration of 
natural quiet once this recommendation is implemented, the NPS further 
recommends that: 

■ The FAA and the NPS work together to develop a process that would 
be initiated when "action triggers" are met as determined through 
the NPS acoustic monitoring program. That is, the FAA and the NPS 
would need to agree on the best course of action to ensure that the 
triggers are not exceeded again. This action must be completed 
within six months of meeting or exceeding the trigger. Limits on 
operations or noise, particularly in flight corridors, would be among 
the measures considered. The FAA would then develop an 
appropriate mechanism (noise budget, co-permitting, or other) that 
would implement this limitation after it has been triggered. 

■ A temporal restriction (a curfew or "no-fly" time period) for 
commercial tour aircraft be implemented on the effective date of a 
new regulation superseding SFAR 50-2. NPS recommends that this 
"no fly" time be from 6 p.m. - 8 a.m. each day. 

■ APIMS ("Aircraft Position Information Monitoring System") or 
similar tracking system be required on Part 135 tour aircraft 
operating in the SFRA for the purpose of tracking compliance, 
numbers of flights per route by time period, and so forth, to develop 
a data base which might be used to develop more effective noise 
abatement techniques. 

10.3.10.4 Flights Outside the SFRA 

The NPS recommends that: 

■ Due to the frequent deviations of high-altitude jets from normal 
routes for sight-seeing purposes, it is recommended that FAA not 
authorize any deviations from normal flight plans and cruising 
altitudes for aircraft on high-altitude jet routes over the Grand 
Canyon area for any reasons other than safety. An FAA study is 
recommended on high-altitude jet routes that may also have impacts 
on natural quiet in the park. 

10.3.10.5 Miscellaneous Recommendations 

The following miscellaneous recommendations are also made: 

■ In those instances where the FAA allows commercial tour aircraft to 
land and take off on lands adjacent to GCNP, the NPS recommends 
the FAA require those aircraft to be at the minimum sector altitude 
prior to crossing over park lands. 



229 



REPORT TO CONGRESS: Conclusions and Recommendations 



■ The FAA, in consultation with the NPS, should revise the "Grand 
Canyon Visual Flight Rules (VFR) Aeronautical Chart" (1st Edition, 
April 4, 1991) at the appropriate time to reflect any changes to the 
SFRA resulting from the previously described recommendations. 

■ The NPS shall establish an interpretive message, exhibit or display(s) 
in key location(s) of the park to describe overflights to visitors, and 
to tell them where they can expect natural quiet and where they can 
expect to hear aircraft. 

■ In recognition of a need for continued cooperation between both the 
FAA and the NPS, a formal process (e.g., a Memorandum of 
Understanding) will need to be established for accommodating 
requests from air tour operators for route changes or other matters 
of interest. 

■ Acknowledging a continuing need for communication between all 
interested parties, the NPS and the FAA should be amenable to 
holding public meetings as needed. 

/ 0.3.1 0.6 Modeling The NPS Recommendation for GCNP 

The NPS recommendation for GCNP was modeled for this report using the 
National Park Overflight Decision Support System — NODSS (Reddingius 
1994). This same system was used previously in evaluating whether natural 
quiet had been substantially restored to GCNP (see Chapter 9, Section 
9.2.3) (also Fidell, Sanford, et. al. 1994). Based on data from a 1989 FAA 
survey of Grand Canyon air tour operators, the NPS modeled the various 
phases of the recommendation. The modeling for each phase takes into 
account forecast increases in the Grand Canyon air tour industry over the 
next 15 years, with some conversions to quiet aircraft. The phases (Year 1, 
Year 5, Year 10, and Year 1 5) are summarized as follows: 

■ Year 1 of the NPS recommendation expands existing flight-free 
zones from 45 to 82 percent of the park. Ceilings of the SFRA and 
flight-free zones are raised to 17,999 feet MSL. About half the 
current SFAR 50-2 tour routes and route segments are eliminated. 
The Dragon Flight Corridor is abolished, but two quiet aircraft 
routes (one for airplanes, one for helicopters) will exist in this area 
(the new Bright Angel Flight-Free Zone) for five years. The Fossil 
Canyon Flight Corridor has been realigned and two-way commercial 
tour traffic eliminated in all flight corridors. The minimum altitude 
for general aviation aircraft in the Tuckup Flight Corridor has been 
lowered from 10,500 feet MSL to 9,500 feet MSL. 



230 



J 0.3 NPS Recommendations to Congress 



■ Year 5 of the NPS recommendation limits the Fossil Canyon Flight 
Corridor to quiet commercial tour aircraft. Quiet aircraft routes 
within the new Bright Angel Flight-Free Zone are eliminated. 

■ Year 10 of die NPS recommendation limits the Zuni Point Flight 
Corridor to quiet commercial tour aircraft. 

■ Year 15 of the NPS recommendation limits the entire SFRA to 
quiet commercial tour aircraft. 

By the year 2010, acoustical modeling predicts that the NPS 
recommendation could substantially restore natural quiet to 
approximately 64 percent of the park (Figure 10.2). As in Chapter 9, 
the white color in Figure 10.2 represents areas of the park where natural 
quiet has been restored 100 percent of the time, green depicts areas restored 
more than 75 percent of the time, and the color red portrays areas of the 
park where natural quiet exists 75 percent of the time or less. Regions ot the 
park classified as "white" and "green" are areas where the NPS considers 
natural quiet to have been substantially restored. 

Acoustic modeling also suggests that by the year 2010, nearly 45 percent ol 
the park could experience natural quiet 100 percent ("white") of the time. 
Figure 10.3 depicts the steady improvement of "100 percent natural quiet" 
at each five-year phase in the form of a bar chart. 

The improvement brought about by the NPS recommendation is especially 
obvious when compared to a "no action" scenario. Modeling this scenario 
for the year 2010 indicates that natural quiet ("white") has been reduced to 
less than 1 percent of the park, down from nearly 45 percent under the NPS 
recommendation. 

10.3.10.7 Summary ofGCNP Recommendation 

As discussed in Chapter 9 (Section 9.2.3) and graphically compared in 
Figure 10.4, unless action is taken to effect the substantial restoration 
brought about by the NPS recommendation, the legislative mandate of P.L. 
1 00 cannot be met. 

It is clear that a "no action" alternative is unacceptable. It is equally clear that 
achieving the substantial restoration mandated by P.L. 100-91 can only be 
accomplished by the proposed restructuring of the space with its larger 
flight- free zones and the gradual conversion of the air tour fleet to quiet 
aircraft, a process already well under way. The 1 5 -year phased approach is 
designed to allow the air tour industry time to acquire such technology, 
either through purchasing new equipment or retrofitting existing equipment. 



231 



REPORT TO CONGRESS: Conclusions and Recommendations 



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232 



10.3 NPS Recommendations to Congress 



50 
40 ■■ 
£ 30 ■• 



5 20 ■ 



10 ■■ 





Natural Quiet 



1989 1995 2000 2005 2010 

For "white" areas (100% natural quiet) on figures 10.4 and )0.5 



Figure 10.3: Percent of GCNP in Natural Quiet (100% 













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60- 
50- 
1 40- 
130- 
20- 
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Figure 10.4: Percent of Park Where Natural Quiet Substantially Restored: 
A Comparison Between NPS Recommendation and No Act/on 



The NPS recommendation extends prompt relief to some areas impacted 
most under SFAR 50-2 and ends with the substantial restoration to natural 
quiet mandated by Public Law 100-91. The NPS position is crafted carefully 
to maintain viable air tour access. The recommendation also offers 
immediate and long-term incentives and rewards to those companies which 
have voluntarily invested in quiet aircraft technology and to those companies 
willing to do so in a timely manner. Access to certain air tour routes over 
Grand Canyon, combined with other economic incentives, could very well 
result in equipment conversions or retrofitting to meet quiet aircraft 
standards within the 1 5-year time frame or sooner. 



233 



REPORT TO CONGRESS: Conclusions and Recommendations 



Results of the acoustic modeling indicate that the sum ot the individual 
recommendations outlined in the preceding sections represent an effective 
approach to effecting and maintaining a substantial restoration of natural 
quiet for GCNP, the legislative mandate in Section 3 of P.L. 100-9 1 . 
Phasing this restoration over time allows for equipment conversions while 
ensuring the continued economic viability of the air tour industry and the 
opportunity for visitors to the area to experience a quality aerial tour. The 
NPS recommendation strikes an appropriate balance between resource 
protection and visitor enjoyment. 



Epilogue v 

Achieving an equitable balance between the impacts and benefits of aviation 
in parks is a difficult but desirable task, one that is still in its infancy. It is a 
long-term goal for both the NPS and FAA to^seek that balance. Prior to the 
establishment of the Department of the Interior — Department of 
Transportation Interagency Working Group and the emerging dialogue 
between the FAA and the NPS, there was no method to address the issue. 
The NPS is confident that with FAA 's continued cooperation and good 
faith, that both agencies will be part of the balanced resolution of potential 
difficulties. It is a new way of doing business for both the NPS and the FAA 
and one that holds promise for the future. 



234 



ffap£risCC)('<2& 




APPENDIX A 



Studies Conducted in Response to P.L. 100-91 

Available Through National Technical Information Service 

The following reports are available through the U.S. Department of Commerce, National Technical Information 
Service, Springfield, VA 22161, telephone (703) 487-4650. The prices and codes shown are accurate to the best of 
our knowledge, with a $3.00 handling charge for each order. Please contact the National Technical Information 
Service direcdy to verify current prices and codes. 

Acoustic Measurements of Sonic Booms and Ambient Sound Levels in the Selway-Bitterroot Wilderness Area. 
NPOA Report No. 90-2. 

NTIS Accession No. PB92- 113505, Paper copy A05 $19.00, Microfiche A01 $9.00. 

Recommendations for Design of Survey Instruments for Public Law 100-91 Field Studies for Summer, 1990. 
NPOA Report No. 90-3. 

NTIS Accession No. PB92- 1 12002, Paper copy A10 $35.00, Microfiche A03 $ 1 7.00. 

Measurements and Analysis of the Indigenous Sound Environment of Coniferous Forests. NPOA Report No. 91-1. 

NTIS Accession No. PB94-151 149, Paper copy A05 $19.50, Microfiche A01 $9.00. 

Short Term Effects of Aircraft Overflights on Outdoor Recreationists in Three Wildernesses. NPOA Report No. 
91-2. 

NTIS Accession No. PB93- 14430 1, Paper copy A09 $27.00, Microfiche A02 $ 12.50. 



237 



APPENDIXES: Appendix A 

Aircraft Noise Effects On Cultural Resources: Review of Technical Literature (3 volumes including Annotated 
Bibliography). NPOA Report No. 91-3. 

NTIS Accession No. PB93-205300, Paper copy E99 $46.58, Microfiche E99 $23.00. 

Effect of Aircraft Altitude Upon Sound Levels at the Ground. NPOA Report No. 91-4. 

NTIS Accession No. PB93-144194, Paper copy A05 $19.50, Microfiche A01 $9.00. 

Intermediate Term Effects of aircraft overflights on Outdoor Recreationists in Twelve Wildernesses. NPOA Report 
No. 91-5. 

(NTIS Accession No. PB 94-151032, Paper Copy A05 $27.00, Microfiche A02 $12.50. 

Aircraft Overflight Study Recommended Plan, Detailed Sampling, Data Collection and Data Analysis Plans for the 
Visitor Survey and the Dose-Response Survey. NPOA Report No. 91-6. 

NTIS Accession No. PB93- 144186, Paper copy A07 $27.00, Microfiche A02 $12.50. 

Estimation of Aircraft Overflight Exposure in National Parks and Forest Service Wildernesses. NPOA Report No. 
92-1. 

NTIS Accession No. PB93-144293, Paper copy A07 $27.00, Microfiche A02 $12.50. 

Detailed Sampling, Data Collection and Analysis Plan for: Air Tour Passenger Survey, NPS Manager Survey, 
General Population Survey. NPOA Report No. 92-3. 

NTIS Accession No. PB93-144285, Paper copy A07, $27.00, Microfiche A02 $12.50. 

Acoustic Data Collected at Grand Canyon, Haleakala and Hawaii Volcanoes National Parks. NPOA Report No. 
93-4. 

NTIS accession No. PB94-149986, Paper copy Al 3 $36.50, Microfiche A03 $17.50. 

Grand Canyon Visitor Survey. NPOA Report No. 93-5. 

NTIS Accession No. PB94-1 54804, Paper copy All, $36.50, Microfiche A03, $17.50. 

Dose-Response Relationships Derived from Data Collected at Grand Canyon, Haleakala and Hawaii Volcanoes 
National Parks. NPOA Report No. 93-6. 

NTIS Accession No. PB94-151941, Paper copy Al 2, $36.50, Microfiche A03, $17.50. 
Survey of National Park Service Managers Related To Aircraft Overflying National Parks. NPOA Report No. 93-7. 

(NTIS Accession No. PB95-105896, Paper Copy A20, $52.00, Microfiche A04, $19.50. 
Aircraft Overflight Effects on Wildlife Resources. NPOA Report No. 93-8. 

NTIS Accession No. PB94-149994, Paper copy A05, $19.50, Microfiche A01, $9.00. 
Aircraft Management Studies, Air Tour Passengers Survey. NPOA Report No. 94-1 

(NTIS Accession No. PB95-104014, Paper Copy Al 2, $36.50, Microfiche A03, $17.50. 



238 



Studies Conducted in Response to P.L. 100-91 

Available through NTIS 

Evaluation of the Effectiveness of SFAR 50-2 in Restoring Natural Quiet to Grand Canyon National Park. NPOA 
Report No. 93-1. 

Sent to NTIS, but no ordering information returned as of publication 
Visitor Survey. NPOA Report No. 94-2. (Three documents: report and appendices in two volumes.) 

Sent to NTIS, but no ordering information returned as of publication. 
Review of the Effects of Aircraft Overflights on Wildlife: Annotated Bibliography. NPOA Report No. 95-1 . 

Sent to NTIS, but no ordering information returned as of publication. 

Reports that will soon be available from NTIS 

Selecting a simplified Method for Acoustic Sampling of Aircraft and Background Sound Levels in National Parks. 
HMMH Report No. 200940.24. 

(Draft) 

"Construction of a Low Noise Easy-to-Use Sound Level Data Collection System Including Simplified Guidelines 
Manual" 

(Draft) 



239 



APPENDIX B 



98 Parks Identified as Potentially Having Overflight Problems 

Parks are listed with the management rank of 1, 2 or 3 (1 being assigned by management to parks in each region 
with the highest severity of aircraft overflight problems) or with an * indicating the park was identified in P.L. 
100-91. 

1 . Agate Fossil Beds National Monument, 1 

2. Antietam National BatdePield, 1 

3. Aposde Islands National Lakeshore, 1 

4. Assateague Island National Seashore, 1 

5. Badlands National Park, 1 

6. Bandelier National Monument, 1 

7. Big Cypress National Preserve, 1 

8. Big Bend National Park, 2 

9. Biscayne National Park, 2 

1 0. Black Canyon of the Gunnison National Monument, 2 

1 1 . Bryce Canyon National Park, 1 

1 2. Cabrillo National Monument, 2 

13. Canaveral National Seashore, 2 

14. Canyon de Chelly National Monument, 1 

15. Cape Lookout National Seashore, 1 

1 6. Cape Cod National Seashore, 1 

17. Cape Hatteras National Seashore, 2 

18. Castillo de San Marcos National Monument, 2 

19. Chaco Culture National Historical Park, 1 

20. Channel Islands National Park, 2 



241 



APPENDIXES: Appendix B 



2 1 . Chattahoochee River National Recreation Area, 2 

22. Chesapeake & Ohio Canal National Historical Park, 1 

23. City of Rocks National Reserve, 2 

24. Colonial National Historical Park, 2 

25. Congaree Swamp National Monument, 2 

26. Coulee Dam National Recreation Area, 2 

27. Crater Lake National Park, 1 

28. Craters of the Moon National Monument, 3 

29. Cumberland Island National Seashore, * 

30. Death Valley National Monument, 1 

3 1 . Devils Tower National Monument, 2 

32. Dry Tortugas National Park, 1 

33. Everglades National Park, 1 

34. Fire Island National Seashore, 1 

35. Fort Vancouver National Historic Site, 1 

36. Fort Washington Park, 3 

37. Fort Sumter National Monument, 2 

38. Fort McHenry National Monument, 2 

39. Fort Union National Monument, 2 

40. Frederick Douglas National Historical Site, 3 

4 1 . Gateway National Recreation Area, 1 

42. George Washington Memorial Parkway, 1 

43. Gettysburg National Military Park, 1 

44. Gila Cliff Dwellings National Monument, 2 

45. Glacier National Park, * 

46. Glen Canyon National Recreation Area, 1 

47. Golden Gate National Recreation Area, 2 

48. Grand Teton National Park, 1 

49. Grand Canyon National Park, * 

50. Great Smoky Mountains National Park, 1 

5 1 . Guadalupe Mountains National Park, 1 

52. Gulf Islands National Seashore, 2 

53. Hagerman Fossil Beds National Monument, 2 

54. Haleakala National Park, * 

55. Hawaii Volcanoes National Park, * 

56. Isle Royale National Park, 1 

57. John Day Fossil Beds National Monument, 2 

58. Joshua Tree National Park, 1 

59. Kalaupapa National Historical Park, 2 

60. Kennesaw Mountain National Batdefield, 2 

6 1 . Kings Canyon & Sequoia National Parks, 1 

62. Lake Chelan National Recreation Area, 1 

63. Lake Mead National Recreation Area, 2 

64. Lassen Volcanic National Park, 2 



242 



98 Porks Identified as Potentially Having Overflight Problems 



65. Mammoth Cave National Park, 2 

66. Manassas National Battlefield Park, 1 

67. Mesa Verde National Park, 2 

68. Minute Man National Historical Park, 1 

69. Mount Rushmore National Memorial, * 

70. Mount Rainier National Park, 1 

7 1 . National Capital Parks - Central, 1 

72. Navajo National Monument, 1 

73. North Cascades National Park, 1 

74. Olympic National Park, 1 

75. Organ Pipe Cactus National Monument, 2 

76. Perry's Victory & International Peace Memorial, 1 

77. Pipe Spring National Monument, 2 

78. Prince William Forest Park, 1 

79. Pu'uhonua o Honaunau National Historical Park, 2 

80. Puukohola Heiau National Historical Site, 2 

8 1 . Rainbow Bridge National Monument, 2 

82. Redwood National Park, 2 

83. Richmond National Batdefield Park, 2 

84. Ross Lake National Recreation Area, 1 

85. Saguaro National Monument, 1 

86. Salinas Pueblo Missions National Monument, 2 

87. San Antonio Missions National Historical Park, 2 

88. Shenandoah National Park, 1 

89. Sleeping Bear Dunes National Lakeshore, 2 

90. Statue of Liberty National Monument, 1 

9 1 . Valley Forge National Historical Park, 1 

92. Voyageurs National Park, 1 

93. White Sands National Monument, 1 

94. Wilson's Creek National Batdefield, 1 

95. Wupatki National Monument, 2 

96. Yosemite National Park, * 

97. Zion National Park, 1 

98. Virgin Islands National Park, 2 



♦(Identified in PL 100-91) 



243 



APPENDIX C 



Legislative Proposals to Control Airspace Over National Park Lands 
H.R. 1696, H.R. 4163, S. 2428 



245 



APPENDIXES: Appendix C 



103d CONGRESS 

1st Session 



H. R. 1696 



To provide for the regulation of the airspace over National Park %stea 
land* in the State of Hawaii by the Federal Aviation Adminirtration 
and the National Park Service, and tor other purposes. 



IN THE HOUSE OP REPRESENTATIVES 

Ann, 5, 1993 
Mr*. Mint introduced the following oill; which was rebrred jointly to the 
Committee* on Natural Resources and Public Work* and Transportation 



A BILL 

To provide for the regulation of the airspace over National 
Park System Lands in the State of Hawaii by the Federal 
Aviation Administration and the National Park Service, 
and for other purposes. 

1 Be it enacted by the Senate and House of Representa- 

2 tives of the United State* of America in Congress assembled, 

3 SECTION 1. nNDIN08, 

4 The Congress finds the following. 

5 (1) The National Park Service administers Fed- 

6 era! parks, monuments, and reservations, to eonserve 

7 the scenery, the natural and historic objects, and 

8 wildlife therein, and provides for the enjoyment of 

C.l 



246 



Legislative Proposals to Control Airspace Over National Park Lands 



2 

1 the same in such manner and by such means as will 

2 leave them unimpaired for the enjoyment of future 

3 generations. 

4 (2) It is the function of the Federal Aviation 

5 Administration to manage the safe and efficient use 

6 of the navigable airspace of the United States, as 

7 provided for in the Federal Aviation Act of 1958 (49 

8 U.S.C. App. 1301 et seq.). 

9 (3) The National Park Service lands in the 

10 State of Hawaii, consisting of Kaloko-Honokohau 

11 National Historical Park, Kalaupapa National His- 

12 torical Park, Pu'u honua o Honaunau National His- 

13 torical Park, Pu'u Kohola Heiau National Historic 

14 Site, Haleakala National Park, and Hawaii Volca- 

15 noes National Park, are managed for the purposes 

16 of wilderness preservation, protecting natural, cul- 

17 tural, historical, and wildlife resources, and for pro- 

18 motion of the public enjoyment and use of these re- 

19 sources. 

20 (4) Haleakala and Hawaii Volcanoes National 

21 Parks are designated by the United Nations as 

22 International Biosphere Reserves because of their 

23 internationally significant scenery and plant and ani- 

24 mal communities, and furthermore that Hawaii Vol- 

25 canoes National Park is designated by the United 

•HR ItM IB 



247 



APPENDIXES: Appendix C 



3 

1 Nations as a World Heritage Site because of the sig- 

2 nificance of Mauna Loa and Kilauea Volcanoes. 

3 (5) In recognition of the values for which Na- 

4 tional Park Service lands are managed, an above 

5 ground level (AGL) minimum altitude of 2,000 feet 

6 shall be established for aircraft flying in airspace 

7 over certain lands administered by the National 

8 Park Service. 

9 (6) The auditory and visual intrusion of aircraft 

10 flying at low altitudes is the source of public com- 

11 plaint in certain areas administered by the National 

12 Park Service. 

13 (7) Aircraft flying at low altitudes may pose a 

14 potential hazard to wildlife in certain areas adminis- 

15 tered by the National Park Service. 

16 (8) Aircraft flying at low altitudes over large 

17 concentrations of migratory birds may pose a poten- 

18 tial safely hazard to pilots and passengers in certain 

19 areas administered by the National Park Service. 

20 (9) The Federal Aviation Administration and 

21 National Park Service shall act in cooperation to re- 

22 duce the incidence of low-flying aircraft, including 

23 fixed-wing aircraft, helicopters, ultralight vehicles, 

24 balloons, and gliders over National Park Service ad- 

25 ministered land by complying with the 2,000 feet 

•BR lew IB 



248 



Legislative Proposals to Control Airspace Over National Park Lands 



4 

1 AGL minimum altitude requirement, and to avoid 

2 flying over areas which the National Park Service 

3 designates as noise-sensitive, and to respect standoff 

4 distances away from areas which the National Park 

5 Service designates as primary visitor use areas. 

6 SEC. 2. NATIONAL PARK SERVICE RESPONSIBILITIES. 

7 The Director of the National Park Service shall be 

8 responsible for the following: 

9 (1) Identification of specific areas. — 

10 Identifying specific areas where low-flying aircraft 

11 may constitute an adverse impact on resources and 

12 conveying specific information, including 'annotated 

13 maps, which indicate designated flight-free areas 

14 and primary visitor use areas, to the Federal Avia- 

15 tion Administration for appropriate action as de- 

16 scribed in section 3. 

17 (2) Low-flying reporting system. — Devel- 

18 oping and implementing a standardized reporting 

19 system acceptable to the Federal Aviation Adminis- 

20 tration to document instances of low-flying aircraft 

21 over National Park Service administered lands. This 

22 reporting system shall provide for transmittal of 

23 such documentation in a timely manner to the Hon- 

24 olulu Federal Aviation Administration Flight Stand- 

25 ards district office. 

•HRMMIH 



249 



APPENDIXES: Appendix C 



5 

1 (3) TRAINING. — Developing training programs 

2 and instructional materials for National Park Serv- 

3 ice personnel to enable them to recognize and report 

4 instances of low-flying aircraft in a competent and 

5 professional manner. The appropriate training pro- 

6 grams of the National Park Service shall expand to 

7 incorporate the subject matter into in-service train- 

8 ing requirements. The Director of the National Park 

9 Service shall seek the assistance of the Federal Avia- 

10 tion Administration to help develop training cur- 

1 1 ricula. 

12 (4) Quarterly meeting. — Making personnel 

13 available from the National Park Service to meet 

14 quarterly with the Federal Aviation Administration 

15 and affected pilots to discuss resources management 

16 objectives and issues associated with low-flying air- 

17 craft. 

1 8 SEC. 3. FEDERAL AVIATION RESPONSIBILITIES. 

19 The Administrator of the Federal Aviation Adminis- 

20 tration shall be responsible for the following: 

21 (1) Communication with pilots. — Commu- 

22 nicating to pilots the concerns and objectives of the 

23 National Park Service about low-flying aircraft in 

24 specified areas, using advisories, bulletins, the Fed- 

25 eral Aviation Administration publication The Fed- 



250 



Legislative Proposals to Control Airspace Over National Park Lands 



6 

1 eral Aviation News, the ongoing "Accident Preven- 

2 tion Program" for routine pilots' contact, and other 

3 means of communications with pilots, and to impress 

4 upon pilots that pilot participation is strongly en- 

5 couraged to ensure protection of resources and the 

6 enjoyment of natural areas by the public. 

7 (2) Investigations. — Investigating instances 

8 of pilot deviations from the Federal Aviation Admin- 

9 istration requested minimum altitude over areas, 

10 and National Park Service-designated flight-free and 

11 primary visitor use areas in lands administered by 

12 the National Park Service, and taking action to dis- 

13 courage deviations with the objectives of reducing or 

14 eliminating such incidents in these areas. 

15 (3) Military aircraft.— Assisting the Na- 

16 tional Park Service in communicating with the var- 

17 ious agencies of the Department of Defense with rer 

18 gard to military aircraft operations over National 

19 Park Service administered areas. 

20 (4) Availability of status and results of 

21 investigations. — Making available to the National 

22 Park Service, at the Federal Aviation Administra- 

23 tion Flight Standards district office, the status and 

24 results of the Federal Aviation Administration's in- 



m 



251 



APPENDIXES: Appendix C 



7 

1 vestigation of instances reported by the National 

2 Park Service. 

3 (5) Support of aviation groups. — Enlisting 

4 the support of all aviation groups and organizations 

5 by requesting they disseminate information about 

6 problems associated with aircraft operating at low 

7 altitudes over areas administered by the National 

8 Park Service. 

9 (6) Meetings with national park serv- 

10 ice. — Assisting the National Park Service in com- 

11 bating problems associated with low-flying aircraft 

12 by participating in appropriate meetings at field and 

13 regional levels. 

14 SEC. 4. flight restriction DESIGNATIONS. 

15 (a) Kaloko Honokohau, Pu'u honua o 

16 HONAUNAU, PU'U KOHOLA HEIAU, AND KALAUPAPA NA- 

17 tional Historical Parks. — Inasmuch as Kaloko 

18 Honokohau, Pu'u honua o Honaunau, Pu'u kohola Heiau, 

19 and Kalaupapa National Historical Parks are mandated 

20 to protect historical, cultural, and religious values, and 

21 other resources considered sacred to Hawaiian people, all, 

22 in their entirety are considered noise-sensitive and shall 

23 not be overflown by commercial tour aircraft. Commercial 

24 fixed-wing aircraft which are not on scenic tours may 

25 overfly Kaloko Honokohau when it is unsafe to use 



m 



252 



Legislative Proposals to Control Airspace Over National Park Lands 



8 

1 alternative approaches to Keahole Airport. Furthermore, 

2 inasmuch as those areas are small and are entirely pri- 

3 mary visitor use areas, scenic tour aircraft shall maintain 

4 a 2-mile standoff distance. 

5 (b) Haleakala National Park. — Inasmuch as 

6 Haleakala National Park is mandated to protect natural 

7 and cultural resources, and especially rare and endangered 

8 plant and animal species, magnificent scenery, and tran- 

9 quil and unique wilderness, the Crater District and 

10 Kipahulu Valley, including adjacent rain forest areas with- 

11 in the Park, in their entirety, are considered noise-sen- 

12 sitive and shall not be overflown. Furthermore, inasmuch 

13 as the overlook near the Sliding Sands trailhead is a pri- 

14 mary visitor use area where people often are assembled 

15 on the ground, a two-mile stand-off distance shall be main- 

16 tained. 

17 (c) Hawaii Volcanoes National Park. — Inas- 

18 much as Hawaii Volcanoes National Park is mandated to 

19 protect natural and cultural resources, and especially rare 

20 and endangered plant and animal species, magnificent sce- 

21 nery, and tranquil and unique wilderness, the designated 

22 wilderness areas, in their entirely, consisting of Mauna 

23 Loa, Ola's Forest, East Rift, and Kau Desert, and the 

24 summit of Kilauea, and the coastal area between Ka'aha 

25 and Kamoarroa are considered noise-sensitive and shall 

•HR isat m 



253 



APPENDIXES: Appendix C 



9 

1 not be overflown. Furthermore, inasmuch as the Kilauea 

2 summit, the Chain of Craters corridor, and the Kamoamoa 

3 village sites are primary visitor use areas where people 

4 often are assembled on the ground, a 2-mile standoff dis- 

5 tance shall be maintained. 

6 (d) Minimum Altitude Restriction. — It shall be 

7 unlawful for any fixed wing aircraft or helicopter flying 

8 under visual flight rules to fly at an altitude of less than 

9 2,000 feet over the surface of any National Park System 

10 lands in the State of Hawaii not subject to subsections 

1 1 (a) through (c) of this section. For purposes of this para- 

12 graph, the term "surface" refers to the highest terrain 

13 within such lands which is within 2,000 feet laterally of 

14 the route of flight. For purposes of enforcement, the pro- 

15 hibition pursuant to this subsection shall be treated as a 

16 requirement established pursuant to section 307 of the 

17 Federal Aviation Act of 1958. To provide information to 

18 pilots regarding the restrictions established under this 

19 subsection, the Administrator of the Federal Aviation Ad- 

20 ministration shall provide public notice of such restrictions 

21 in appropriate Federal Aviation Administration publica- 

22 tions as soon as practicable after the enactment of this 

23 Act 



•HR 1«M m 



254 



Legislative Proposals to Control Airspace Over National Park Lands 



10 

1 8EC. 5. FEDERAL AVIATION ADMINISTRATION AND NA- 

2 TIONAL PARK SERVICE JOINT RESPONSIBIL- 

3 rnr. 

4 The Administrator of the Federal Aviation Adminis- 

5 tration and the Director of the National Park Service shall 

6 jointly be responsible for the following: 

7 (1) Additional assessments. — Assess situa- 

8 tions in addition to those specified in section 4 

9 where impacts of aircraft operations upon human, 

10 cultural, or natural resources are sufficiently serious 

11 to warrant consideration of site-specific action by 

12 the Federal Aviation Administration to minimize or 

13 eliminate the causes of such problems. 

14 (2) Informational materials and sci- 

15 ENTTFIC STUDIES. — Prepare public informational 

16 materials, including printed matter and audio-visual 

17 programs, for communication to pilots using existing 

18 Federal Aviation Administration pilot-contact meet- 

19 ings and programs, aviation periodicals, and other 

20 means of generating pilot understanding of National 

21 Park Service resources management objectives. 

22 Where appropriate, the Federal Aviation Adminis- 

23 tration and the National Park Service will share in- 

24 formation on techniques of conducting scientific 

25 studies and data collection to facilitate understand- 

•HR ]«• IH 



255 



APPENDIXES: Appendix C 



11 

1 ing of the impact of aircraft operations on affected 

2 resources. 

3 (3) Procedures.— Work together to define 
.4 procedures for use at national headquarters and 
'5 field office levels to address overflight issues over 

6 public land areas. 

7 SEC. 6. APPLICABILITY OF CERTAIN REGULATIONS TO-CER- 

8 TAIN SIGHTSEEING FLIGHTS. • 

9 Parts 91 and 135 of title 14 of the Code of Federal 

10 Regulations, relating to general operating and flight rules 

11 and to air taxi operators and commercial operators, re- 

12 spectively, shall apply to nonstop sightseeing flights that 

13 begin and end at the same airport and aiv conducted with- 

14 in a 25 statute mile radius of the airport. 

O 



•HH 1«M IB 



256 



Legislative Proposals to Control Airspace Over National Park Lands 



103d congress 
2d Session 



H.R.4163 



To enable the Park Service to regulate, or prohibit, icenie commercial 
overflights at units of the National Park System. 



IN THE HOUSE OF REPRESENTATIVES 

March 24, 1994 
Mr. Williams (for himself, Mrs. Mink, Mr. DeFazio, Ms. Shepherd, Mr. 
Upton, and Mr. STARK) introduced the following bill; which was referred 
jointly to the Committees on Natural Resources and Public Works and 
Transportation 



A BILL 

To enable the Park Service to regulate, or prohibit, scenic 
commercial overflights at units of the National Park System. 

1 Be it enacted by the Senate and House of Representa- 

2 tives of the United States of America in Congress assembled, 

3 SECTION 1. SHORT TITLE. 

4 This Act may be cited as the "National Park Scenic 

5 Overflight Concessions Act of 1994". 

6 SEC. 2. PURPOSE AND FINDINGS. 

7 (a) PURPOSE. — The purpose of this Act is to require 

8 all commercial air tour operators to hold a concessions 

9 permit with the Park Unit, and to provide Park Service 



257 



APPENDIXES: Appendix C 



2 

1 authority to determine the appropriate level of commercial 

2 scenic tour overflight activity. 

3 (b) FINDINGS.— The Congress finds that: 

4 (1) The National Park Service administers Fed- 

5 eral parks, monuments, and reservations, to conserve 

6 the scenery; natural, cultural and historic values; 

7 wilderness values, including natural quiet; and wild- 

8 life resources while providing for the enjoyment of 

9 the same in such manner and by such means as will 

10 leave them unimpaired for the enjoyment of future 

11 generations. In recognition of these values, many 

12 park units are recognized as internationally signifi- 

13 cant International Biosphere Reserves and World 

14 Heritage Sites. 

15 (2) In order to manage National Park System 

16 units to achieve the purposes for which they were es- 

17 tablished by Congress, there is a need for National 

18 Park Service authority to regulate commercial scenic 

19 overflight enterprises operating over units of the 

20 National Park system. 

21 (3) It is the function of the Federal Aviation 

22 Administration to manage the safe and efficient use 

23 of the navigable airspace of the United States, as 

24 provided for in the Federal Aviation Act of 1958 (49 

25 U.S.C. App. 1391, et seq.); and to protect the envi- 

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Legislative Proposals to Control Airspace Over National Park Lands 



3 

1 ronment from adverse impacts in accord with sec- 

2 tions 307(c) and 611 of the foregoing Act and sec- 

3 tion 4(f) of the Department of Transportation Act 

4 (49 U.S.C. 1653(f)). 

5 (4) The auditory and visual intrusion of aircraft 

6 flying at low altitudes can be incompatible with the 

7 preservation and management of natural or cultural 

8 resources, the natural quiet, scenery, and/or the 

9 public's enjoyment of the resources on lands man- 

10 aged by the public land management agencies, nota- 

11 bly such sensitive areas as parks, wildlife refuges, 

12 and wilderness areas. 

13 (5) It is the joint responsibility of these agen- 

14 cies to resolve these incompatible situations or miti- 

15 gate them to the fullest extent possible in order to 

16 maintain these public lands for the purposes for 

17 which they were established while recognizing the 

18 public's and the Government's need to transit navi- 

19 gable airspace. 

20 (6) In recognition of the values for which Na- 

21 tional Park Service lands are managed, the Federal 

22 Aviation Administration and the National Park 

23 Service shall act cooperatively to reduce the inci- 

24 dence of low-flying aircraft impacts from commercial 

25 scenic tour overflights by helicopters, fixed-wing air- 



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APPENDIXES: Appendix C 



4 

1 craft, blimps, and balloons over sensitive lands ad- 

2 ministered by the National Park Service and to 

3 make these overflights compatible with park preser- 

4 vation objectives. 

5 SEC. 3. COMMERCIAL AIR TOURS. 

6 The Act of October 9, 1965 (16 U.S.C. 20-20g) com- 

7 monly known as the National Park Service Concessions 

8 Policy Act is amended by adding the following new section 

9 at the end thereof: 

10 "SEC. 10. COMMERCIAL AIR TOURS OVER NPS UNITS. 

11 "(a) Issuance of Permits for Commercial Am 

12 Tours. — No person may fly an individual for compensa- 

13 tion over any unit of the National Park System for the 

14 purpose of viewing any portion of such unit unless such 

15 person has in effect a valid commercial air tour permit 

16 issued by the Secretary. The Secretary may issue or deny 

17 such permits upon application of any person. Such permits 

18 may be issued subject to such conditions and restrictions 

19 as the Secretary deems necessary to protect the resources 

20 of such unit and to protect and enhance visitor enjoyment. 

21 Issuance or denial of a permit shall be consistent with the 

22 legislation establishing such unit, the guidelines under 

23 subsection (b), any applicable provisions of any genera) 

24 management plan in effect for such unit, and the provi- 

25 sions of law generally applicable to units of the national 

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Legislative Proposals to Control Airspace Over National Park Lands 



5 

1 park system, including the Act of August 25, 1916 (39 

2 Stat. 535; 16 U.S.C. 1, 2, 3, and 4) and the Act of August 

3 21, 1935 (49 Stat. 666; 16 U.S.C. 461-467). Any person 

4 who flies an individual for compensation over any unit of 

5 the National Park System for the purpose of viewing any 

6 portion of such unit shall be treated as entering such unit 

7 and providing a service within such unit for purposes of 

8 this Act. This subsection shall take effect on the date one 

9 year after the enactment of the National Park Scenic 

10 Overflight Concessions Act of 1994 and shall apply to all 

11 flights described in this subsection made after such effec- 

12 tivedate. 

13 "(b) Guidelines and Planning.— Not later than 

14 12 months after the enactment of this Act, the Secretary 

15 shall publish guidelines applicable to commercial air tour 

16 flights over national park system units providing {or such 

17 flights where appropriate and restricting or prohibiting 

18 such flights where necessary in accordance with the provi- 

19 sions of law referred to in subsection (a). Each permit 

20 under subsection (a) for flights at any unit of the National 

21 Park System shall be based on such guidelines. Any such 

22 guidelines proposed by the Secretary shall be submitted 

23 to the Administrator of the Federal Aviation Administra- 

24 tion for review prior to adoption. Within 60 days after 

25 his receipt of such proposed guidelines, the Administrator 

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6 

1 shall provide comments and recommendations to the Sec- 

2 retaiy regarding any effects such guidelines may have on 

3 aircraft safety. The Secretary shall incorporate the Ad- 

4 ministrator's recommendations regarding aircraft safety 

5 in the final guidelines. 

6 "(c) General Management Plans.— The Sec- 

7 retary may amend the general management plan for any 

8 national park system unit to establish air concessjons re- 

9 quirements applicable to flights subject to the permit re- 

10 quirements of subsection (a). Such amendments shall be 

11 consistent with the provisions of law referred to in sub- 

12 section (a) and the guidelines published under subsection 

13 (b). The amendments shall — 

14 "(1) document the degree to which commercial 

15 scenic overflights may affect the natural resources of 

16 the park unit concerned; 

17 "(2) document the effects of such overflights on 

18 the park visitor's experience; and 

19 "(3) propose measures necessary to protect 

20 park resources and the visitor's experience from the 

21 adverse effects of commercial scenic overflights. 

22 Each permit issued under subsection (a) for flights over 

23 any national park system unit after the effective date of 

24 general management plan amendments adopted under this 

25 subsection shall be consistent with such amendments. 

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7 

1 "(d) PENALTY.— Any person who knowingly or will- 

2 fully violates any requirement of this section or of any rule 

3 or regulation promulgated by the Secretary under this sec- 

4 tion shall be fined not more than $5,000 or imprisoned 

5 for not more than 5 years or both.". 

6 SEC. 4. FEDERAL AVIATION ADMINISTRATION 

7 (a) Reporting and Training. — The Administrator 

8 of the Federal Aviation Administration (hereinafter in this 

9 section referred to as the "Administrator"), in cooperation 

10 with the Secretary of the Interior, shall — 

11 (1) develop standardized reporting systems for 

12 the documentation of low flying aircraft incidents in 

13 air space over national park system units; and 

14 (2) develop training programs and instructional 

15 materials for national park service personnel to en- 

16 able them to recognize and report instance of low 

17 flying aircraft incidents in air space over national 

18 park system units. 

19 (b) Aircraft Noise. — The Administrator shall 

20 amend the regulations of the Federal Aviation Administra- 

21 tion to treat aircraft noise abatement at national park sys- 

22 tern units as in the public interest. 

23 (c) Reports. — The Administrator and the Secretary 

24 of the Interior shall submit a joint report to the Congress 

25 within 3 years after the enactment of this Act containing 

•HR <1«3 m 



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APPENDIXES: Appendix C 



103d CONGRESS 
2d Session 



S. 2428 



To provide for the management of the airspace over the units of the National 
Park System, and for other purposes. 



IN THE SENATE OP THE UNITED STATES 

AUGUST 25 (legislative day, AUGUST 18), 1994 

Mr. Axaka introduced the following bill; which was read twice and referred 

to the Committee on Commerce, Science, and Transportation 



A BILL 

To provide for the management of the airspace over the 
units of the National Park System, and for other purpose • 

1 Be it enacted by the Senate and House of Reprem uta- 

2 tives of the United States of America in Congress assembled, 

3 SECTION 1. SHORT TITLE. 

4 This Act may be cited as the "National Parks Air- 

5 space Management Act of 1994". 

6 SEC. 2. FINDINGS. 

7 Congress makes the following findings: 

8 (1) Air tour flights over units of the National 

9 Park System may have adverse effects on such 
10 units. 



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2 

1 (2) Congressional concern over the effects of 

2 low-level flights on the units of the National Park 

3 System led to the enactment of the Act entitled "An 

4 Act to require the Secretary of the Interior to con- 

5 duct a study to determine the appropriate minimum 

6 altitude for aircraft flying over national park system 

7 units", approved August 18, 1987 (Public Law 100- 

8 91; 101 Stat. 674; 16 U.S.C. la-1 note). The Act 

9 required the Director to identify problems associated 

10 with flights by aircraft in the airspace over the units 

11 of the National Park System. 

12 (3) The number of flights by aircraft over units 

13 of the National Park System has increased rapidly 

14 since the enactment of the Act, and the National 

15 Park Service continues to struggle to develop a pol- 

16 icy which would achieve an acceptable balance be- 

17 tween flights over such units by commercial air tour 

18 operators and the protection of the resources in such 

19 units and the experiences of visitors to such units. 

20 (4) Visitors to certain units of the National 

21 Park System may reasonably expect quiet during 

22 their visits to such units, particularly visitors to 

23 units established with the specific goal of providing 

24 visitors to the units with an opportunity for solitude. 



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APPENDIXES: Appendix C 



3 

1 (5) Natural quiet is an inherent resource of cer- 

2 tain units of the National Park System. It is in the 

3 public interest that natural quiet at such units be 

4 conserved in the same manner as other resources 

5 under the care and jurisdiction of the National Park 

6 Service. 

7 (6) The public has registered a significant num- 

8 ber of complaints about commercial air tour flights 

9 over certain areas under the jurisdiction of the Na- 

10 tional Park Service. 

11 (7) Such flights may degrade the experiences of 

12 visitors to the affected areas and may have adverse 

13 effects on wildlife and cultural resources in such 

14 areas. 

15 (8) The Federal Aviation Administration con- 

16 tinues to have difficulty controlling adequately com - 

17 mercial air tour flights by aircraft over units of the 

18 National Park System that are adversely affected by 

19 such flights. 

20 (9) There are significant and continuing con- 

21 cerns about the safety of commercial air tour flights 

22 over some units of the National Park System, in- 

23 eluding concerns for the safety of occupants of the 

24 flights, of visitors to such units, of Federal Govern- 



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Legislative Proposals to Control Airspace Over National Park Lands 



4 

1 ment employees at such units, and of the general 

2 public. 

3 SEC. 3. MINIMIZATION OF EFFECTS OF COMMERCIAL AIR 

4 TOUR FLIGHTS OVER UNITS OF THE NA- 

5 TIONAL PARK SYSTEM. 

6 (a) PROHIBITION ON FLIGHTS BELOW CERTAIN AL- 

7 TITUDES. — (1) Notwithstanding any other provision of law 

8 and subject to paragraph (2), a commercial air tour opera- 

9 tor may not conduct the portion of a commercial air tour 

10 flight that takes place over a unit of the National Park 

11 System at an altitude that is less than 3,000 feet above 

12 ground level. 

13 (2) The prohibition in paragraph (1) may not be con- 

14 strued to prohibit an agreement among a commercial air 

15 tour operator, the Administrator, and the Director which 

16 establishes a minimum flight altitude for commercial air 

17 tour flights of the operator over a particular unit of the 

18 National Park System that differs from the minimum 

19 flight altitude set forth in that paragraph. 

20 (b) Additional Actions To Minimize Effects. — 

21 Notwithstanding any other provision of law, the Adminis- 

22 trator and the Director shall jointly take such actions as 

23 the Administrator and the Director determine appropriate 

24 in order — 



•S 8438 is 



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APPENDIXES: Appendix C 



5 

1 (1) to determine the most practical and effec- 

2 tive means of minimizing the effects of commercial 

3 air tour flights over units of the National Park Sys- 

4 tern; 

5 (2) to implement such means; and 

6 (3) to conduct periodic training of the employ- 

7 ees of the Federal Aviation Administration and the 

8 National Park Service on matters relating to the im- 

9 plementation of such means. 

10 SEC. 4. DEVELOPMENT OF SINGLE STANDARD FOR CER- 

11 TD7YING COMMERCIAL AIR TOUR OPERA- 

12 TORS. 

13 (a) Commencement of Rulemaking. — Not later 

14 than 90 days after the date of the enactment of this Act, 

15 the Administrator shall initiate formal rulemaking proce- 

16 dures for the purpose of prescribing a new subpart of part 

17 135 of title 14, Code of Federal Regulations (relating to 

18 air taxi operators and commercial operators), which would 

19 specifically cover all commercial air tour operators (as that 

20 term will be defined by the Federal Aviation Administra- 

2 1 tion under the subpart) that conduct commercial air tour 

22 flights over units of the National Park System. 

23 (b) Covered Matters. — The subpart prescribed 

24 under subsection (a) shall contain regulations that address 

25 safety and environmental issues with respect to commer- 

•S S42S IS 



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Legislative Proposals to Control Airspace Over National Park Lands 



6 

1 cial air tour flights over units of the National Park Sys- 

2 tern. In prescribing the subpart, the Administrator shall 

3 attempt to minimize the financial and administrative bur- 

4 dens imposed on commercial air tour operators by such 

5 regulations. 

6 (c) Completion. — The Administrator shall — 

7 (1) complete prescription of the regulations re- 

8 ferred to in subsection (a) not later than the end of 

9 the 1-year period beginning on the date of the enact- 

10 ment of this Act; or 

11 (2) if the Administrator does not complete the 

12 prescription by the end of that period, submit to 

13 Congress a report at the end of that period which 

14 report shall — 

15 (A) provide an explanation of the failure of 

16 the Administrator to complete the prescription 

17 within that period; and 

18 (B) describe the status of the regulations 

19 to be prescribed. 

20 SEC. 5. DEVELOPMENT OF OPERATIONAL RULE FOR COM- 

21 MERCIAL AIR TOUR OPERATIONS OVER 

22 UNITS OF THE NATIONAL PARK SYSTEM. 

23 (a) Requirement. — (1) Except as provided in para- 

24 graph (2), the Administrator shall initiate formal rule- 

25 making procedures for the purpose of prescribing a single 

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APPENDIXES: Appendix C 



7 

1 operational rule which would govern the conduct of fixed 

2 wing and rotorcraft flights by commercial air tour opera- 

3 tors over the units of the National Park System. The Ad- 

4 ministrator shall initiate such procedures not later than 

5 90 days after the date of the enactment of this Act. 

6 (2) The Administrator may prescribe separate oper- 

7 ational rules governing the conduct of flights by fixed-wing 

8 aircraft and by rotorcraft if the Administrator determines 

9 under subsection (b)(1) that separate rules are warranted. 

10 (b) Considerations. — In developing an operational 

1 1 rule under subsection (a), the Administrator shall — 

12 (1) consider whether differences in the charac- 

13 teristics and effects on the environment of fixed- 

14 wing aircraft and rotorcraft warrant the develop- 

15 ment of separate operational rules with respect to 

16 such craft; 

17 (2) provide a mechanism for the Director to 

18 recommend individual units or geographically proxi- 

19 mate groups of units to be designated as aerial 

20 sightseeing areas, as defined by Federal Aviation 

21 Administration Handbook 92.01, dated January 

22 1992; and 

23 (3) provide a mechanism for the Director to ob- 

24 tain immediate assistance from the Administrator in 

25 resolving issues relating to the use of airspace above 

•S 1428 18 



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Legislative Proposals to Control Airspace Over National Park Lands 



8 

1 units which issues are of a critical, time-sensitive na- 

2 ture. 

3 (c) Completion. — The Administrator shall — 

4 (1) complete prescription of the regulations re- 

5 ferred to in subsection (a) not later than the end of 

6 the 1-year period beginning on the date of the enact- 

7 ment of this Act; or 

8 (2) if the Administrator does not complete the 

9 prescription by the end of that period, submit to 

10 Congress a report at the end of that period which 

1 1 report shall — 

12 (A) provide an explanation for the failure 

13 of the Administrator to complete the prescrip- 

14 tion within that period; and 

15 (B) describe the status of the regulations 

16 to be prescribed. 

17 (d) Effect - on Agreements. — Nothing in this sec- 

18 tion is intended to preclude the Administrator, the Direc- 
19- tor, and a commercial air tour operator from entering into 

20 an agreement under section 7 (including an agreement 

21 under subsection (c)(3) or (d)(1) of that section) on the 

22 conduct of air tour flights by the air tour operator over 

23 a particular unit of the National Park System under dif- 

24 ferent terms and conditions than those imposed by the 

25 operational rule or rules prescribed under this section. 

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APPENDIXES: Appendix C 



9 

1 SEC. 6. FLIGHT-FREE PARKS. 

2 (a) Designation op Units. — Not later than 1 year 

3 after the date of the enactment of this Act, the Director, 

4 in consultation with the Administrator, shall — 

5 (1) prescribe criteria to identify units of the 

6 National Park System where air tour flights by com- 

7 mercial air tour aircraft are incompatible with or in- 

8 jurious to the purposes and values for which" such 

9 units were established; 

10 (2) identify any units of the National Park Sys- 

1 1 tem which meet such criteria; and 

12 (3) designate such units as units of the Na- 

13 tional Park System covered by this section. 

14 (b) Requirements Relating to Criteria. — In 

15 prescribing criteria under subsection (a), the Director — 

16 (1) shall ensure sufficient opportunity for public 

17 comment; 

18 (2) shall give due consideration to the com- 

19 ments and recommendations of the National Park 

20 Overflight Advisory Council established under sec- 

21 tion 10 and of the Federal Interagency Airspace/ 

22 Natural Resource Coordination Group, or any suc- 

23 cessor organization to that entity; and 

24 (3) may utilize the authority to engage in nego- 

25 tiated rulemaking under subchapter in of chapter 5 

26 of title 5, United States Code. 

S 2428 IS 2 



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Legislative Proposals lo Control Airspace Over National Park Lands 



10 

1 (c) Effect of Designation. — 

2 (1) Prohibition. — Except as provided in para- 

3 graphs (2) and (3), commercial air tour flights may 

4 not be conducted in the airspace over any unit of the 

5 National Park System designated under subsection 

6 (a)(3). 

7 (2) Operators conducting flights before 

8 1994. — 

9 (A) In general. — Subject to subpara- 

10 graph (B) and paragraph (4), a commercial air 

11 tour operator that conducted commercial air 

12 tour flights in the airspace over a unit des- 

13 ignated under subsection (a)(3) as of December 

14 31, 1993, may continue to conduct flights in 

15 that airspace. 

16 (B) Limitation. — The number of com- 

17 mercial air tour flights over a unit that a com- 

18 mercial air tour operator may conduct under 

19 this paragraph in any year after 1994 may not 

20 exceed the number of such flights that the oper- 

21 ator conducted over the unit during 1993. 

22 (3) Operators commencing flights after 

23 1993. — 

24 (A) In general.— -Subject to subpara- 

25 graph (B) and paragraph (4), a commercial air 

•s ua is 



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APPENDIXES: Appendix C 



11 

1 tour operator that commences, during the pe- 

2 riod beginning on January 1, 1994, and ending 

3 on the date of the enactment of this Act, the 

4 conduct of commercial air tour flights in the 

5 airspace over a unit designated under sub- 

6 section (a)(3) may continue to conduct flights 

7 in that airspace. 

8 (B) Limitation. — The number of com- 

9 mercial air tour flights over a unit that a com- 

10 mercial air tour operator may conduct under 

11 this paragraph in any month after December 

12 1994 may not exceed the average number of 

13 flights per month that the operator conducted 

14 over the unit during the period referred to in 

15 subparagraph (A). 

16 (4) Effect of sale or discontinuation of 

17 operations. — 

18 (A) Prohibition on sale. — The author- 

19 ity of a commercial air tour operator to conduct 

20 commercial air tour flights under paragraph (2) 

21 or (3) may not be sold, conveyed, or otherwise 

22 transferred. 

23 (B) Discontinuation. — Upon the dis- 

24 continuation by a commercial air tour operator 

25 of commercial air tour flights over a unit of the 



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Legislative Proposals to Control Airspace Over National Park Lands 



12 

1 National Park System under paragraph (2) or 

2 (3), the authority of the air tour operator to 

3 conduct such flights over that unit shall termi- 

4 nate. 

5 SEC. 7. FLIGHTS OVER OTHER UNITS OF THE NATIONAL 

6 PARK SYSTEM. 

7 (a) National Park Airspace Management 

8 Plans. — 

9 (1) In general. — The Director and the Ad- 

10 ministrator shall establish in accordance with this 

11 subsection a plan for the management of the air- 

12 space above each unit of the National Park System 

13 not designated under section 6 that — 

14 (A) is affected by commercial air tour 

15 flights to such an extent that the Director con- 

16 siders the unit to be a unit requiring an air- 

17 space management plan; or 

18 (B) is a unit over which — 

19 (i) no commercial air tour flights oc- 

20 curred on or before the date of the enact* 

21 ment of this Act; and 

22 (ii) a commercial air tour operator 

23 proposes to conduct commercial air tour 

24 flights after that date. 



•8 MM 18 



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APPENDIXES: Appendix C 



13 

1 (2) Plan purpose. — The purpose of a plan 

2 under this subsection is to minimize the adverse ef- 

3 fects of commercial air tour flights on the resources 

4 of a unit of the National Park System. 

5 (b) Development of Airspace Management 

6 Plans. — 

7 (1) In general. — 

8 (A) Affected units. — The Director and 

9 the Administrator shall jointJy develop a plan 

10 for the management of the airspace above a 

1 1 unit of the National Park System referred to in 

12 subsection (a)(1)(A) not later than 1 year after 

13 the date of the determination by the Director 

14 under that subsection that the unit requires 

15 such a plan. 

16 (B) Units subject to proposed oper- 

17 ATIONS. — In the case of a unit referred to in 

18 subsection (a)(1)(B), the Director and the Ad- 

19 ministrator shall jointly develop a plan for the 

20 management of the airspace over the unit not 

21 later than 180 days after the date on which a 

22 commercial air tour operator first submits to 

23 the Director a proposal referred to in that sub- 

24 section. The proposal shall include any informa- 

25 tion that the Director and the Administrator 

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Legislative Proposals to Control Airspace Over National Park Lands 



14 

1 consider necessary in order to evaluate fully the 

2 proposal. 

3 (2) Treatment of relevant expertise. — In 

4 developing plans under paragraph (1), the Adminis- 

5 trator shall defer to the Director in matters relating 

6 to the identification and protection of park re- 

7 sources, and the Director shall defer to the Adminis- 

8 trator in matters relating to the safe and efficient 

9 management of airspace. 

10 (3) Negotiated rulemaking. — In developing 

11 a plan for a unit, the Director and the Adminis- 

12 trator shall jointly — 

13 (A) determine whether the utilization of 

14 negotiated rulemaking procedures under sub- 

15 chapter m of chapter 5 of title 5, United 

16 States Code, in the development of the plan is 

17 in the public interest; and 

18 (B) if the Director and the Administrator 

19 determine that such utilization is in the public 

20 interest, develop the plan utilizing procedures 

21 for such rulemaking under that subchapter. 

22 (4) Comment on plans. — In developing a plan 

23 for a unit, the Director and the Administrator 

24 shall— 



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APPENDIXES: Appendix C 



15 

1 (A) ensure sufficient opportunity for public 

2 comment; and 

3 (B) give due consideration to the com- 

4 ments and recommendations of the National 

5 Park Overflight Advisory Council established 

6 under seetion 10 and the Federal Interagency 

7 Airspace/Natural Resource Coordination Group, 

8 or any successor organization to that entity. 

9 (5) Resolution of plan inadequacies— If 

10 the Director and the Administrator disagree with re- 

11 spect to any portion of a proposed plan under this 

12 subsection, the Director and the Administrator shall 

13 refer the proposed plan to the Secretary of the Inte- 

14 rior and the Secretary of Transportation who shall 

15 jointly resolve the disagreement. 

16 (6) Assessment op effects of 

17 OVERFLIGHTS. — The Director and the Administrator 

18 may jointly conduct any studies to ascertain the ef- 

19 fects of low-level flights of commercial air tour air- 

20 craft over units of the National Park System that 

21 the Director and the Administrator consider nee- 

22 essary for the development of plans under this sub- 

23 section. 

24 (7) Periodic review. — The Director and the 

25 Administrator shall periodically review each plan de- 

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Legislative Proposals to Control Airspace Over National Park Lands 



16 

1 veloped under this subsection. The purpose of the re- 

2 view is to ensure that the plan continues to meet the 

3 purpose of the plan under this subsection. The Di- 

4 rector and the Administrator may revise a plan if 

5 they determine based on such review that such revi- 

6 sion is advisable. 

7 (c) Flights Over Units Requiring Management 

8 Plans. — 

9 (1) Flights over units covered by 

10 plans. — A commercial air tour operator may not 

11 conduct commercial air tour flights in the airspace 

12 over a unit of the National Park System covered by 

13 an airspace management plan developed under sub- 

14 section (b) unless the commercial air tour operator 

15 enters into an agreement with respect to the conduct 

16 of such flights under paragraph (3). 

17 (2) Flights pending development of 

18 plans. — 

19 (A) Flights by existing operators. — 

20 (i) In general. — A commercial air 

21 tour operator described in clause (ii) may 

22 conduct commercial air tour operations in 

23 the airspace over a unit described in that 

24 clause -during the period of the develop- 

25 ment of an airspace management plan for 

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APPENDIXES: Appendix C 



17 

1 the unit under this section. The number of 

2 such flights during any day in that period 

3 may not exceed the average daily number 

4 of commercial air tour flights conducted by 

5 the air tour operator during the 12 -month 

6 period ending on the date of the com- 

7 mencement of the development of the plan 

8 under this section. 

9 (ii) Covered operators. — Clause (i) 

10 applies to any commercial air tour operator 

11 that conducts commercial air tour flights 

12 over a unit of the National Park System 

13 for which the Director determines under 

14 subsection (a) that an airspace manage- 

15 ment plan is required if the commercial air 

16 tour operator conducts such flights over 

17 the unit as of the date of that determina- 

18 tion. 

19 (B) Flights by potential opera- 

20 TORS. — Except as provided in subparagraph 

21 (A), a commercial air tour operator may not 

22 conduct commercial air tour flights over a unit 

23 of the National Park System referred to in 

24 clause (ii) of that subparagraph during the pe* 

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Legislative Proposals to Control Airspace Over National Park Lands 



18 

1 riod referred to in clause (i) of that subpara- 

2 graph. 

3 (3) Agreement. — An agreement referred to in 

4 paragraph (1) is an agreement among a commercial 

5 air tour operator, the Director, and the Adminis- 

6 trator which provides for the application of relevant 

7 provisions of the airspace management plan for the 

8 unit concerned to the commercial air tour operator 

9 entering into the agreement. 

10 (d) Flight Over Units Not Requiring Manage- 

11 ment Plans. — 

12 (1) Requirement for agreement. — A com- 

13 mercial air tour operator may not conduct commer- 

14 cial air tour flights over a unit of the National Park 

15 System for which no airspace management plan is 

16 required under this section unless the commercial air 

17 tour operator enters into an agreement with the Di- 

18 rector and the Administrator relating to the conduct 

19 of such flights. The terms and conditions of the 

20 agreement shall, to the maximum extent practicable, 

21 provide for the conduct of air tour flights by the air 

22 tour operator in a manner that minimizes the ad- 

23 verse effect of such air tour flights on the environ- 

24 ment of the unit. 



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APPENDIXES: Appendix C 



19 

1 (2) Flights pending agreement. — A com- 

2 mercial air tour operator that conducts commercial 

3 air tour flights over a unit referred to in paragraph 

4 (1) on the date of the enactment of this Act may 

5 continue to conduct such flights during negotiations 

6 for the agreement referred to in paragraph (1). The 

7 number of such flights during any day in that period 

8 may not exceed the average daily number of com- 

9 mercial air tour flights conducted by the air tour op- 

10 erator during the 12-month period ending on the 

11 date of the commencement of negotiations for the 

12 agreement. 

13 (e) Resolution of Disputes in Entering Into 

14 Agreements. — 

15 (1) Resolution. — In the event of a dispute be- 

16 tween a commercial air tour operator and the Direc- 

17 tor and the Administrator during entry into an 

18 agreement under subsection (c) or (d), the Director, 

19 the Administrator, and the air tour operator shall 

20 attempt to resolve the dispute using the dispute res- 

21 olution proceedings authorized under subchapter IV 

22 of chapter 5 ot title 5, United States Code. 

23 (2) Failure op resolution. — If the Director, 

24 the Administrator, and a commercial air tour opera- 

25 tor are unable to resolve a dispute referred to in 

•8 S43S 18 



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Legislative Proposals to Control Airspace Over National Park Lands 



20 

1 paragraph (1) using the dispute resolution proce- 

2 dures referred to in that paragraph, the Adminis- 

3 trator shall prescribe an operational rule for the unit 

4 of the National Park System concerned in accord- 

5 ance with subsection (f)(3). 

6 (f) Oversight. — 

7 (1) Assessment of effectiveness of 

8 AGREEMENTS. — The Director shall periodically carry 

9 out such studies as are necessary to determine if 

10 agreements entered into under subsections (c) and 

11 (d) are adequate to minimize the adverse effects of 

12 commercial air tour flights on the resources of the 

13 units of the National Park System covered by such 

14 agreements. 

15 (2) Response to inadequacy. — If the Direc- 

16 tor determines under paragraph (1) that one or 

17 more agreements referred to in that paragraph are 

18 inadequate to minimize the effects referred to in 

19 that paragraph, the Director shall — 

20 (A) notify the Administrator and the com- 

21 mercial air tour operator concerned of that de- 

22 termination; and 

23 (B) attempt to resolve the inadequacy uti- 

24 lizing the dispute resolution procedures author- 



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APPENDIXES: Appendix C 



21 

1 ized under subchapter IV of chapter 5 of title 

2 5, United States Code. 

3 (3) Additional resolution authority. — 

4 (A) Operational rule.— If the Director, 

5 the Administrator, and a commercial air tour 

6 operator are unable to resolve an inadequacy in 

7 an agreement utilizing the dispute resolution 

8 procedures referred to in paragraph (2)(B), the 

9 Administrator shall prescribe an operational 

10 rule for the unit concerned. The purpose of the 

11 rule shall be to minimize the adverse effects of 

12 commercial air tour flights on the resources of 

13 the unit concerned. 

14 (B) Disputes relating to rule. — If the 

15 Director determines that the implementation of 

16 an operational rule, and the enforcement there- 

17 of by the Administrator, is inadequate in whole 

18 or in part to minimize the adverse effects of 

19 commercial air tour flights on the resources of 

20 the unit concerned, the Director shall — 

21 (i) notify the Administrator and the 

22 commercial air tour operator or operators 

23 concerned of that determination; and 

24 (ii) attempt to resolve the inadequacy 

25 utilizing the dispute resolution procedures 

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Legislative Proposals to Control Airspace Over National Park Lands 



22 

1 authorized under subchapter IV of chapter 

2 5 of title 5, United States Code. 

3 (C) Final resolution. — If the Director, 

4 the Administrator, and the commercial air tour 

5 operator or operators concerned are unable to 

6 resolve an inadequacy in an operational rule 

7 under subparagraph (B), the Administrator 

8 shall develop a Special Federal Aviation Regula- 

9 tion (SFAR) covering the unit concerned. 

10 SEC. 8. FLIGHTS BY OTHER AIRCRAFT OVER UNITS OF THE 

1 1 NATIONAL PARK SYSTEM. 

12 (a) Flight Emergencies. — No provision of this Act 

13 shall apply to an aircraft experiencing an in-flight emer- 

14 gency. 

15 (b) Flights by Military Aircraft. — Notwith- 

16 standing any other provision of law, military aircraft may 

17 not conduct flights in the airspace over a unit of the Na- 

18 tional Park System below an altitude that is 3,000 above 

19 ground level, except as provided for in a Memorandum of 

20 Understanding between the Director and the Secretary of 

21 Defense. 

22 (c) Flights for Commercial Aerial Photog- 

23 raphy.— 

24 (1) In general. — An aircraft or rotorcraft en- 

25 gaged in commercial aerial photography may not 

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APPENDIXES: Appendix C 



> 23 

1 conduct flights in the airspace over a unit of the Na- 

2 tional Park Service below an altitude that is 3,000 

3 feet above ground level unless the pilot of the air- 

4 craft or rotorcraft receives advance written permis- 

5 sion from the appropriate Flight Standards District 

6 Office of the Federal Aviation Administration and 

7 from the superintendent of the unit of the National 

8 Park System concerned. 

9 (2) Fees. — The superintendents of the units of 

10 the National Park System may collect fees from the 

1 1 operators of aircraft and rotorcraft engaged in com- 

12 mercial aerial photography. The fees shall be set at 

13 such amount as the Director determines necessary to 

14 ensure that the United States will receive fair mar- 

15 ket value for the use of the area concerned and 

16 shall, at a minimum, cover all administrative and 

17 other costs of providing necessary services associated 

18 with commercial aerial photography at such units. 

19 SEC. ». AIRCRAFT SAFETY. 

20 (a) Aircraft Markings. — 

21 (1) Requirement. — Each operator of commer- 

22 cial air tour aircraft shall display on each air tour 

23 aircraft of the operator the identification marks de- 

24 scribed in paragraph (2). 



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Legislative Proposals to Control A/rspoce Over National Park Lands 



24 

1 (2) Identification marks. — The identifica- 

2 tion marks for the aircraft of a commercial air tour 

3 operator shall — 

4 (A) be unique to the operator; 

5 (B) be not less than 36 inches in length 

6 (or a size consistent with the natural configura- 

7 tion of the aircraft fuselage); 

8 (C) appear on both sides of the air tour 

9 aircraft of the air tour operator and on the un- 

10 derside of the aircraft; and 

11 (D) be applied to the air tour aircraft of 

12 the air tour operator in a highly visible color 

13 that contrasts sharply with the original base 

14 color paint scheme of the aircraft. 

15 (b) Flight Monitoring Systems.— 

16 (1) Requirement for study. — Not later than 

17 1 year after the date of the enactment of this Act, 

18 the Administrator shall carry out a study of the fea- 

19 sibility and advisability of requiring that aircraft and 

20 rotorcraft operating in the airspace over units of the 

21 National Park System have onboard an automatic 

22 flight tracking system capable of monitoring the alti- 

23 tude and ground position of the aircraft and rotor- 

24 craft. 



•s «a 18 



287 



APPENDIXES: Appendix C 



25 

1 (2) Installation op plight monitoring 

2 system. — If the Administrator determines under the 

3 study required under paragraph (1) that the use of 

4 automatic flight tracking system in aircraft and 

5 rotorcraft is feasible and advisable, then not later 

6 than 2 years after the date of the enactment of this 

7 Act, each commercial air tour operator that conducts 

8 air tour flights in the airspace above a unit Of the 

9 National Park System shall have an automatic flight 

10 tracking system onboard each aircraft and rotorcraft 

11 of such air tour operator that conducts such air tour 

12 flights. 

13 (3) Monitoring through systems. — 

14 (A) Monitoring. — The Director shall en- 

15 sure that appropriate personnel of the National 

16 Park Service monitor the altitude and position 

17 of aircraft and rotorcraft, if any, having a sys- 

18 tern required under paragraph (2) for purposes 

19 of determining that the aircraft and rotorcraft 

20 - comply with all laws, regulations, and agree- 

21 ments on flights in the airspace over units of 

22 the National Park System. 

23 (B) Violations. — The Director shall en- 

24 sure that personnel referred to in subparagraph 

25 (A) report to the Federal Aviation Administra- 

\ 

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Legislative Proposals to Control A/rspoce Over National Park Lands 



26 

1 tion any apparent violations of the laws and 

2 regulations referred to in that subparagraph. 

3 (e) Aeronautical Charts. — The Administrator 

4 shall ensure that the boundaries of each unit of the Na- 

5 iional Park System and the provisions of the airspace 

6 management plan, operational rule, or Special Federal 

7 Aviation Regulation (SFAR), if any, with respect to each 

8 such unit are accurately reflected on aeronautical charts. 

9 (d) Park Visitor Education. — The Director shall 

10 develop educational materials for public distribution on air 

1 1 tour flights over units of the National Park System by 

12 commercial air tour operators. Such materials shall in- 

13 dude the most common flight patterns and routes of such 

14 flights. 

15 (e) Data Collection.— 

16 (1) In general. — The Administrator shall col- 

17 lect and publish each year statistical data on com- 

18 mercial air tour flights over the units of the Na- 

19 tional Park System. 

20 (2) Requirement for information.— The 

21 information collected under paragraph (1) shall in- 

22 elude the following: 

23 (A) The units at which such flights oc- 

24 curred. 



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APPENDIXES: Appendix C 



27 

1 (B) The flight hours flown during such 

2 flights. 

3 (C) The number of passengers carried dur- 

4 ing such flights. 

5 (D) The number and type of aircraft 

6 safety violations that occurred during such 

7 flights. 

8 (E) The number and type of accidents or 

9 other incidents involving air tour aircraft that 

10 occurred during such flights. 

11 (F) The number and type of disciplinary 

12 actions, if any, taken against the pilots of such 

13 aircraft with respect to such flights. 

14 SEC. 10. NATIONAL PARK OVERFLIGHT ADVISORY 

15 COUNCIL. 

16 (a) Establishment. — There is hereby established a 

17 commission to be known as the National Park Overflight 

18 Advisory Council (in this section referred to as the "Coun- 

19 cil"). 

20 (b) Membership. — 

21 (1) Voting members. — The Council shall be 

22 composed of 20 voting members appointed jointly by 

23 the Director and the Administrator as follows: 



•s ma is 



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Legislative Proposals to Control Airspace Over National Park Lands 



28 

1 (A) Five representatives of environmental 

2 or conservation organizations, citizens' groups, 

3 and other groups with similar interests. 

4 (B) Five representatives of the commercial 

5 air tour industry and organizations with similar 

6 interests. 

7 (C) Five individuals from the private sec- 

8 tor who — 

9 (i) have an interest in the effects on 

10 the units of the National Park System of 

11 , -commercial air tour flights in the airspace 

12 over such units; 

13 (ii) are not affiliated with the organi- 

14 zations or groups referred to in subpara- 

15 graph (A) or the industry or organizations 

16 referred to in subparagraph (B); and 

17 (iii) have no substantial financial in- 

18 teres t in the management of the airspace 

19 over units of the National Park System. 

20 (D) Five representatives of departments or 

21 agencies of the Federal Government (other than 

22 individuals associated with the Department of 

23 the Interior and the Department of Transpor- 

24 tation), with the consent of the head of the de- 

25 partment or agency concerned, who have regu- 

«s mm is 



291 



APPENDIXES: Appendix C 



29 

1 latory responsibility over land management 

2 matters, airspace management matters, or both. 

3 (2) Ex officio members. — The Director, or 

4 the designee of the Director, and the Administrator, 

5 or the designee of the Administrator, shall be ex 

6 officio members of the Council. 

7 (3) Appointment date. — Members of the 

8 Council shall be appointed under this subsection not 

9 later than 90 days after the date of the enactment 

10 of this Act. 

11 (4) Selection of chair. — The Council shall 

12 elect a Chairperson from among the voting members 

13 of the Council. 

14 (5) Meetings. — The Council shall first meet 

15 not later than 180 days after the date of the enact- 

16 ment of this Act and shall meet thereafter at the call 

17 of a majority of the members of the Council. 

18 (c) Duties. — The Council shall have the following 

19 duties: 

20 (1) To determine the effects on the environment 

21 of units of the National Park System of commercial 

22 air tour flights in the airspace over such units. 

23 (2) To determine the economic effects of re- 

24 strictions or prohibitions on such flights. 



•8 MZS IS 



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Legislative Proposals to Control Airspace Over National Park Lands 



30 

1 (3) To solicit and receive comments from inter- 

2 e&ted individuals and groups on such flights. 

3 (4) To develop recommendations for means of 

4 reducing the adverse effects of such flights on such 

5 units. 

6 (5) To explore financial and other incentives 

7 which could encourage manufacturers to advance the 

8 state-of-the-art in quiet aircraft and rotorcraft tech- 

9 nology and encourage commercial air tour operators 
ID to implement such technology in flights over park 

11 units. 

12 (6) To provide comments and recommendations 

13 to the Director and the Administrator under sections 

14 6 and 7. 

15 (7) To provide advice or recommendations to 

16 the Director, the Administrator, and other appro- 

17 priate individuals and groups on matters relating to 

18 such flights. 

19 (8) To carry out such other activities as the Di- 

20 rector and the Administrator jointly consider appro- 

21 priate. 

22 (d) Administration.— 

23 (1) Compensation of non-federal mem- 

24 bers. — Members of the Council who are not officers 

25 or employees of the Federal Government shall serve 

•B «u IS 



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APPENDIXES: Appendix C 



31 

1 without compensation for their work on the Council, 

2 but shall be allowed travel expenses, including per 

3 diem in lieu of subsistence, in the same manner as 

4 persons employed intermittently in the Government 

5 service under section 5703(b) of title 5, United 

6 States Code, to the extent funds are available there- 

7 for. 

8 (2) Compensation op federal members. — 

9 Members of the Council who are officers or employ- 

10 ees of the Federal Government shall serve without 

11 compensation for their work on the Council other 

12 than that compensation received in their regular 

13 public employment, but shall be allowed travel ex- 

14 penses, including per diem in lieu of subsistence, as 

15 authorized by law, to the extent funds are available 

16 therefor. 

17 (3) Administrative support. — The Director 

18 and the Administrator shall, to the extent permitted 

19 by law, provide the Council with such administrative 

20 services, funds, facilities, staff and other support 

21 services as may be necessary for the performance of 

22 its functions. 

23 (e) REPORTS. — The Council shall annually submit to 

24 Congress, the Administrator, and the Director a report 

25 that— 

•8*428 18 



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Legislative Proposals to Control Airspace Over National Park Lands 



\ 



32 

1 (1) describes the activities of the Council under 

2 this section during the preceding year, and 

3 (2) sets forth the findings and recommenda- 

4 tions of the Council on matters related to the jniti- 
5< gation of the effects on the units of the National 
6' Park System of flights of commercial air tour opera- 

7 tors over such units. 

8 (f) Authorization of Appropriations.— There 

9 are authorized to be appropriated such sums as may be 

10 necessary to carry out the provisions of this section. 

11 SEC. 11. DEFINITIONS. 

12 In this Act: 

13 (1) The term "Administrator" means the Ad- 

14 ministrator of the Federal Aviation Administration. 

15 (2) The term "air tour aircraft" means an air- 

16 craft (including a fixed-wing aircraft or a rotorcraft) 

17 that makes air tour flights. 

18 (3) The term "air tour flight" means a pas- 

19 senger flight conducted by aircraft (including by 

20 fixed-wing aircraft or by rotorcraft) for the purpose 

21 of permitting a passenger to the flight to view an 

22 area over which the flight occurs. 

23 (4) Except as defined by the Federal Aviation 

24 Administration under section 4, the term "commer- 

25 cial air tour operator" means a company, COrpOra- 
tf USS IS 



295 



APPENDIXES: Appendix C 



33 

1 tion, partnership, individual, or "ther entity that 

2 provides air tour flights for hire to the public. 

3 (5) The term "Director" means the Director of 

4 the National Park Service. 

O 



•8 UU 18 



296 



APPENDIX D 



Advanced Notice of Proposed Rulemaking Issued Jointly by Federal Aviation 
Administration and National Park Service 



297 



APPENDIXES: Appendix D 




Thursday 
March 17, 1994 




Part IV 

Department of 
Transportation 

Federal Aviation Administration 
14 CFR Parts 91 and 135 

Department of the 
Interior 

National Park Service 

36 CFR Part 1, et al. 

Overflights of Units of the National Park 

System; Proposed Rule 



298 



Advance Notice of Proposed Rulemaking Issued Jointly by FAA and NPS 



12740 



Federal Register / Vol. 59, No. 52 / Thursday, March 17, 1994 / Proposed Rules 



DEPARTMENT OF TRANSPORTATION 
Federal Aviation Administration 
14 CFR Parts 91 and 13S 
DEPARTMENT OF THE INTERIOR 
National Park Service 
30 CFR Parts 1, 2, 3, 4, 5, 6 and 7 
[Docket No. 27843; Notk* No. 94-*] 

Overnights of Units ot the National 
Park System 

AGENCY: National Park Service (NPS). 
DOI and Federal Aviation 
Administration (FAA), DOT. 
ACTION: Advanced notice of proposed 
rulemaking (ANPRM). 

SUMMARY: This notice seeks public 
comment on general policy and specific 
recommendations for voluntary and 
regulatory actions to address the effects 
of aircraft overflights on national parks. 

On December 22, 1993, 
Transportation Secretary Federico Pena 
and Interior Secretary Bruce Babbitt 
announced the formation of an 
interagency working group to explore 
ways to limit or reduce impacts from 
overflights on national parks. Secretary 
Babbitt and Secretary Pena concur that 
increased flight operations at the Grand 
Canyon and other national parks have 
significantly diminished the national 
park experience for park visitors, and 
that measures can and should be taken 
to preserve n quality park experience for 
visitors. The Secretaries see the 
formation of the working group, and the 
mutual commitment to addressing the 
impacts of park overflights, as the initial 
steps in a new spirit of cooperation 
between the two departments. 

National parks are unique national 
resources that have been provided 
special protection by law. The National 
Park Service (NPS) and the Federal 
Aviation Administration (FAA) 
recognize that excessive noise from 
commercial air tours and other flights 
over units of the national parks system 
can interfere with NPS efforts to achieve 
a natural park experience for visitors 
and to preserve other park values. 
Through the interagency working group, 
the NPS and FAA will cooperate in 
developing measures to resolve current 
noise impacts and prevent potential 
future impacts from overflights at 
national parks. The purpose of this 
ANPRM is twofold. First, the ANPRM 
addresses overflights of Grand Canyon 
National Park and national parks in the 
State of Hawaii, with particular 
emphasis on overflights by commercial 



tour operators. Second, the ANPRM 
solicits policy views and 
recommendations on more general 
issues as part of an effort to form a 
comprehensive policy on preventing, 
minimizing, or eliminating impacts of 
aircraft overflights. 

This notice presents options that may 
be considered as means to minimize the 
advene effects of commercial air tour 
operations and other overflights on 
units of the national park system, -and 
seeks public comments and suggestion^ 
on voluntary and regulatory actions to 
deal with noise and other overflight - 
issues that may affect national -park«j 
dates: Comments on this ANPRM*nru*t 
be received on or before June 16, 1094.' 
addresses: Comments on this advance i 
notice should be mailed, in triplicate, ' 
to: Federal Aviation Administration, 
Office of Chief Counsel,- Attention) 
Rules Docket (AGC-200). Docket No.' 
27643, 600 Independence Avenue; SWV, 
Washington, DC 20591. Comments 
delivered must be marked Docket No. 
27643. Comments may be examined in 
room 915G weekdays between i8'.30 a.m. 
and S p.m., except on Federal hblidaytv 
FOR FURTHER INFORMATION CONTACT: 
David L. Bennett Office of Chief 
Counsel, AGC-600, Federal Aviation' 
Administration, 800 Independence 
Avenue, SW . Washington. DC 20591, 
telephone (202) 267-3473, or Michael 
M. Tiernan, Office of the Solicitor, 
Department of Interior (DOI), 18th and 
C Streets, NW., Washington, DC 20240. 
telephone (202) 208-7597. 

SUPPLEMENTARY INFORMATION: 



Invited 

Interested persons are invited to 
participate in this advance notice of 
proposed rulemaking by submitting 
such written data, views, or arguments 
as they may desire. Comments relating 
to the policy, environmental, energy, 
federalism, or economic impact that 
might result from considering the 
options in this advance notice are also 
invited. Comments should identify the 
regulatory docket number and should be 
submitted in triplicate to the Rules 
Docket address specified above. All 
comments received on or before the 
specified closing data for comments will 
be considered by NPS and FAA before 
taking action on this advanced notice of 
proposed rulemaking. All comments 
received will be available, both before 
and after the closing date for comments, 
in the Rules Docket for examination by 
interested persons. Commenters wishing 
the FAA or NPS to acknowledge receipt 
of their comments submitted in 
response to this notice must include a 
preaddressed, stamped postcard on 



which the following statement is made: 
"Comments to Docket No. 27643." The 
postcard will be date stamped and 
mailed to the commenter. 

Availability of ANPRM 

Any person may obtain a copy of this 
ANPRM by submitting a request to the 
Federal Aviation Administration. Office 
of Public Affairs, Attention: Public 
Inquiry Center, APA-200, 800 
Independence Avenue, SW., 
Washington, DC 20591. or by calling 
(202) 2G 7-3485. Communications must 
identify the notice number of this 
ANPRM 

Background 

The management of the national park 
system is guided by the Constitution, 
public laws (Pub. L.). proclamations. 
executive orders, rules and regulations, 
and directives of the Sec retary of the 
Interior and the Assistant Secretary for 
Fish and Wildlife and Park*; The Act of 
August 25, 1916, otherwise known a* 
the NPS Organic Act, established the 
NPS and serves as the touchstone for 
national park system management 
philosophy and policy. The Act created 
the NPS to promote and regulats 
national parks, monuments, and 
reservations in accordance with the 
fundamental purpose of said parks, 
monuments, snd reservations, which is 
"to conserve the scenery and the natural 
and historic objects and the wildlife 
therein and to provide for the enjoyment 
of the same in such manner and by such 
means as will leave them unimpaired 
for the enjoyment of future 
generations." (16 U.S.C. 1). Subsequent 
legislation further states that any 
authorized activity "shall not be 
exercised in derogation of the values 
and purposes" of a park area or the 
national park system, except as may 
have been or shall be directly and 
specifically provided by Ha^ieae (16 
U.S.C. la-1). 

Thus, "unimpairment" is joined by a 
responsibility to avoid derogation not 
only of the purposes of a park area but 
also the values for which the national 
park system and its individual units 
have been established. 

In 19S7. the Congress enacted the NPS 
Overflights Act because it recognized 
that aircraft overflights can adversely 
affect national parks. The Act 
specifically found that noise associated 
with aircraft overflight at the Grand 
Canyon National Park was causing "a 
significant adverse effect on the natural 
quiet and experience of the park and 
current operations at the Grand Canyon 
National Park have raised serious 
concerns regarding safety of park users." 
(Pub. L. 100-91. section 3(a)). The Act 



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APPENDIXES: Appendix D 



Federal Register / Vol. 59, No. 52 / Thursday, March 17, 1994 / Proposed Rules 12741 



mandated a number of studies related to 
the effects of overflights on parks. The 
studies have taken longer than was 
originally anticipated because many of 
the Issues with which they deal are on 
the cutting edge of technical and 
scientific capability. Measuring degrees 
of quiet and perception of quiet is very 
different from measuring amounts of 
noise. Since the Overflights Act was 
passed, the adverse effects associated 
with the numbers and extent of 
commercial air sightseeing tours have 
continued to expand. 

The general and over-arching 
responsibilities for park management by 
NPS may be modified by specific 
direction in individual enabling 
legislation and proclamations. The 
individual statutes and proclamations 
for some units of the national park 
system make it clear that the units were 
established to provide visitors with 
natural quiet, an opportunity for 
solitude, and other attributes that are 
not necessarily compatible with the 
noise of commercial air tour sightseeing 
flights. Some people simply find 
commercial sightseeing tours over parks 
inappropriate and incompatible with 
protection of certain park values and 
resources. On the other hand, a 
commercial air tour may provide an 
opportunity for people to see some park 
resources in ways not otherwise 
attainable. 

As is pointed out in the Management 
Policies (NPS 1988): 

Over the years, legislative and 
administrative actions have bean taking place 
that have brought some measure of change to 
these components of our national parks. Such 
ectlooj Impact park resources, yet they are 
not necessarily deemed to have impaired 
reaources for the enjoyment of future 
generations. Whether an individual action Is 
or is not an "impairment" is a management 
determination based on NPS policy. In 
reaching it, the manager should consider 
auch factors as the spatial and temporal 
extent of the impacts, the resources being 
impacted and their ability to adjust to those 
impacts, the relation of the impacted 
reaources to other park resources, and the 
cumulative as well aa the individual effects. 

Both physical resources, such as 
wildlife or geologic features or cultural 
resources, and intangible values, such as 
natural quiet solitude, and the 
experience of wilderness, can be 
impaired. 

Impacts to Parks 

In the case of commercial air tour 
sightseeing flights operating over and 
near units of the national park system, 
the NPS believes that significant park 
resources are being Impaired in some 
units. Managers of almost one-third of 
national park system units perceive a 



problem with some aspect of already 
existing aircraft overflights- The sound 
of aircraft is regarded as the primary 
impact. A survey of park managers 
confirmed that mechanical noise is 
among the more serious problems in 
parks and aircraft noise is the most 
prominent among these. The perception 
of noise and adverse effects in units of 
the national park system may be related 
to the fact that parks tend to be quieter 
places in general and that typical 
sources of noise found in urban and 
suburban settings are absent in most 
parks. The potential exists for 
impairment of park resources and 
values by the noise and visual intrusion 
associated with commercial air tour/ 
sightseeing operations in other units 
where the air tour sightseeing industry 
is not yet established or developed. 

Given the changes in our population 
distribution, patterns of use of our 
national parks, and other factors related 
to transportation, it is no longer 
sufficient for park managers to consider 
strategies and actions solely within park 
boundaries to protect parks and their 
resources. Overflights are a case in 
point. Most overflights of units of the 
national park system begin and end at 
airports outside parks; the attractions 
the overflights offer are the resources of 
the parks themselves. Technically, the 
park overflight passenger is not a park 
visitor even though there may be 
significant adverse effects from noise on 
the park. In recognition of this fact, the 
FAA and the NPS are working more 
closely to use the FAA's plenary 
authority for regulation of aviation in 
support of NPS management objectives. 

FAA Authorities 

The FAA has broad authority and 
responsibility to regulate the operation 
of aircraft and the use of the navigable 
airspace, and to establish safety 
standards for and regulate the 
certification of airmen, aircraft, and air 
carriers. (Federal Aviation Act of 1958, 
as amended (FAAct). Section 307(a) and 
(c); Title VI.) The FAAct provides 
guidance to the Administrator in 
carrying out this responsibility. Section 
1 02 of the FAAct states that the 
Administrator will consider the public 
interest to include among other things, 
regulation for safety and efficiency of 
both civil and military operations, 
promotion of the development of civil 
aviation, fulfillment of the requirements 
of national defense, and operation of a 
common system of air traffic control for 
civil and military aircraft. Section 104 
provides to each citizen of the United 
States a public right of transit through 
the navigable airspace of the United 
States. Section 305 directs and 



authorizes the Administrator to 
encourage and foster the development of 
civil aeronautics and air commerce. 
Section 306 requires the Administrator 
in exercising his authority, to give full 
consideration to the requirements of 
national defense, commercial and 
general aviation, and to the public right 
of freedom of transit through the 
navigable airspace. 

The FAA's authority is not limited to 
regulation for aviation safety, efficiency, 
and development. Subsection 307(c) of 
the FAAct provides that FAA air traffic 
rules and flight regulations may be 
adopted "for the protection of persons 
and property on the ground." The FAA 
considers this protection to extend to 
environmental values on the surface as 
well as to the safety of persons and 
property. Section 611 of the FAAct. "in 
order to affdfti present and future relief 
to the public health and welfare from 
aircraft noise." directs the 
Administrator to adopt regulations "as 
the FAA may find necessary for the 
control and abatement of aircraft noise," 
including application of such 
regulations to any of the various 
certificates issued under Title VI. 
Finally, it is the general policy of the 
Federal government that the FAA, like 
other agencies, will exercise its 
authority In a manner that will enhance 
the environment, and that the FAA will 
make a special effort to preserve the 
natural beauty of public park and 
recreation lands, wilderness areas, and 
wildlife refuges. Section 101 of the 
National Environmental Policy Act of 
1969, as amended. 42 U.S.C 4321: 
Section 4(0 of the Department of 
Transportation Act. 49 U.S.C. 303; and 
Executive Order 11514. as amended by 
Executive Order 1 1991. In addition, the 
DOT has further authority to regulate 
services by commercial operators. 

Fee* 

The Budget Reconciliation Act of 
1993 (Pub. L. 103-66, August 10, 1993) 
amended Section 4 of the Land and 
Water Conservation Fund Act of 1965 
(16 U.S.C. 4601-6a) requiring the NPS 
to impose a commercial tour use fee on 
each vehicle entering a unit of the 
national park system, that presently 
charges an entrance fee, for the purpose 
of providing commercial tour services. 

In addition to surface transportation, 
this commercial use fee applies to 
aircraft entering "the airspace of units of 
the National Park System" identified In 
sections 2(b) and 3 of Public Law 100.91 
(Grand Canyon National Park and 
Haleakala National Park) as well as any 
other park areas where the level of 
commercial aircraft services are equal to 



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or greater than these two identified 
areas. 

The actual fees established by the 
legislation are as follows: 

• $25 per vehicle with a capacity of 
25 people or less, and 

• $50 per vehicle with a capacity 
greater than 25 people. The legislation 
also gives the Secretary the authority to 
make reasonable adjustments to these 
recommended commercial tour fees. 
Currently, there are no additional NPS 
areas that charge entrance fees, and also 
have a level of commercial aircraft 
services equal or greater to Grand 
Canyon or Haleakala National Parks. As 
a result of the legislation, the NPS will 
need to monitor the number of air tour 
operations over the affected parks. 

Grand Canyon National Park 

At Grand Canyon, 42 companies offer 
aerial tours operating from five states 
(Arizona, California, Nevada, Utah, and 
New Mexico). These companies provide 
air tours of the Grand Canyon to about 
750.000 people and generate revenues 
in excess of $100 million. During peak 
summer months, the number of tours 
exceeds 10.000 each month. On June 5. 
1987, the FAA issued Special Federal 
Aviation Regulation (SFAR) No. SO-l 
(52 FR 22734. June 15. 1987) which 
provided rules to enhance safety of 
overflight operations in the vicinity of 
the Grand Canyon National Park. 
Section 3 of Public Law 100-91 required 
the Secretary of the Department of the 
Interior (DO!) to submit to the FAA 
Administrator recommendations for the 
protection of resources in the Grand 
Canyon from adverse impacts associated 
with aircraft overflights. The 
recommendations were to provide for 
substantial restoration of the natural 
quiet and experience of the Grand 
Canyon. With limited exceptions, the 
recommendations were to prohibit the 
flight of aircraft below the rim of the 
Canyon and to designate zones that 
were flight free except for purposes of 
administration of underlying lands and 
emergency operations. 

Public Law 100-91 further required 
the Secretary of the Interior to prepare 
and issue a final plan for the 
management of air traffic above the 
Grand Canyon. In December 1987. the 
DOI submitted recommendations to the 
FAA for an aircraft management plan at 
the Grand Canyon. The 
recommendations included both 
rulemaking and non-rulemaking actions. 
On May 27. 1988, the FAA issued SFAR 
No. 50-2 (53 FR 20264. June 2. 1988) 
which revises the procedures for 
operation of aircraft in the airspace 
above the Grand Canyon. The rule 
implements the preliminary 



recommendations of the Secretary of the 
Interior for an aircraft management plan 
at the Grand Canyon with some 
modifications that the FAA initiated in 
the interest of aviation safety. SFAR No. 
50-2 establishes a Special Flight Rules 
Area from the surface to 14,500 feet 
above mean seal level (MSL) in the area 
of the Grand Canyon. The SFAR 
prohibits flight below a certain altitude 
in each of five sactors or this area with 
some exceptions. The SFAR also 
establishes flight free zones from the 
surface to 14,500 feet msl above large 
areas of the park. The "flight free zones" 
cover virtually all of the visitors to the 
North and South Rims and about 90 
percent of backcountry users. The SFAR 
also provided special routes for 
commercial tour operators and transient 
operators through the canyon area. 
Commercial air tour operations are 
required to be conducted as air taxi and 
commercial operations under part 135 
with stringent requirements including 
special operations specifications for 
Grand Canyon. The NPS believes the 
SFAR has been successful in limiting 
some noise-associated adverse impacts 
to the park but most, if not all. of the 
gain has been, or may be, lost as a result 
of the exponential growth in numbers of 
flights over the canyon. 

Virtually every class of visitor activity 
at Grand Canyon National Park is 
limited or controlled in some way by 
the NPS to insure that there will be no 
derogation or impairment of resources 
and values. Each raft trip on the 
Colorado River through Grand Canyon 
National Park must have a permit and 
the number of permits is limited for 
both commercial and private rafters. For 
some private raft trips, a permit may 
take 4 or 5 years to obtain. Each over- 
night visitor in the backcountry must 
have a backcountry permit; the demand 
for such permits far exceeds the supply. 
The waiting list for trips by mule Into 
the inner canyon runs into years for 
some times of the year. There are a 
limited number of hotel rooms In the 
park and there are a limited number of 
parking spaces, in contrast, the 
commercial air tour sector has 
experienced unlimited growth at Grand 
Canyon National Park in the last 10 
years. This is so even though Congress 
found noise associated with overflights 
to be significantly and adversely 
affecting the park in the 1987 
Overflights Act. In addition, the NPS 
believes there is ample evidence that the 
uncontrolled and unregulated growth in 
this sector is in derogation of the 
resources and values of the park. NPS 
studies to that effect will be published 
later this year. 



Grand Canyon — Actions to Date 
Public Law 100-91 directed the DOI 

to substantially restore "natural quiet" 
to the Grand Canyon National Park. 
Public Law 100-91 also required a study 
of aircraft noise impacts at a number of 
national parks and imposed flight 
restrictions at three parks: Grand 
Canyon National Park, Yosemite 
National Park in California, and 
Haleakala National Park in Hawaii. 
Public Law 100-91 also required the 
DOI to conduct a study, with the 
technical assistance of the Secretary of 
Transportation, to determine the proper 
minimum altitude to be maintained by 
aircraft when flying over units of the 
national park system. The research was 
to include an evaluation of the noise 
levels associated with overflights. 
Before submission to Congress, the DOI 
is to provide a draft report (containing 
the results of its studies) and 
recommendations for legislative and 
regulatory action to the FAA for review. 
The FAA is to notify the DOI of any 
adverse effects these recommendations 
would have on the safety of aircraft 
operations. The FAA is to consult with 
the DOI to resolve these issues. The 
final report must include a finding by 
the FAA that implementation of the DOI 
recommendations will not have adverse 
effects on the safety of aircraft 
operations, or, in the alternative, a 
statement of the reasons why the 
recommendations will have an adverse 
effect. The DOI expects to complete the 
report by early summer, 1994. 

Haleakala and Hawaii Volcanoes 
National Parks 

The national parks in Hawaii — Hawaii 
Volcanoes and Haleakala — have similar 
problems with commercial air 
sightseeing tours, principally noise 
associated with helicopters. The FAA 
held a series of public hearings in 
January 1994 to elicit public comments 
and recommendations for regulatory or 
policy action related to overflights, 
including their effects on parks. There 
are 9 tour operators on the island of 
Hawaii, and there are approximately 60 
commercial air tours a day over Hawaii 
Volcanoes National Park. At Haleakala, 
which was established to preserve 
resources in "natural condition," (39 
Stat. 432, section 4), seven companies 
based on the island of Maui offer 
helicopter tours. On clear days, 
helicopters fly over the park during all 
hours of daylight so that helicopter 
noise is audible over 30 minutes of 
every daylight hour (personal 
communication. Haleakala National 
Park). Interpretive talks, wildlife 
observations and censuses, ceremonies. 



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and other normal activities are 
interrupted by air tour overflights. The 
NPS recognizes that the commercial air 
tour industry is important to the 
economy of Hawaii but also believes 
that the tourism industry benefits from 
the continued NPS protection of the 
superlative resources of its national 
parks, unimpaired. 

Hawaii — Actions to Date 

The majority of flights conducted by 
helicopter companies in Hawaii are 
commercial air tour/sightseeing 
operations. Both the NPS and FAA have 
received numerous complaints of 
commercial air sightseeing tour flights 
over residential communities, national 
parks, wildlife refuge areas. State 
natural reserve areas, sanctuaries and 
areas of significant histonc or cultural 
value. Issues raised by the growth of air 
tour sightseeing activity and the 
associated increase in the number of 
flights conducted over a given area 
include aircraft noise, flight noise, flight 
safety, and airport site constraints near 
scenic areas. It may be necessary to 
determine if there are thresholds of 
adverse effects that have been met in 
terms of impacts to the parks. 

The FAA has taken several steps to 
address the overflight issues in Hawaii. 
In 1986. the FAA conducted a study of 
helicopter sightseeing operations in 
Hawaii. As a result of that study, 
recommendations were made to the 
State and to operators in Hawaii to 
improve safety and community 
relations. Also in 1986. the FAA 
conducted a joint study with the State 
on heliport and airport access. A result 
of that study was a helicopter operating 
plan for Hawaii. Numerous meetings 
have since been held with NPS 
personnel, industry, and local 
communities, including four public 
meetings conducted in January 1994 

Impacts to Parks and Their Resources 

At some parks, including Grand 
Canyon National Park. Hawaii 
Volcanoes National Park, and Haleakala 
National Park, the temporal and spatial 
extent of commercial air tours are, in the 
judgment of NPS managers, impairing 
park resources and visitor experience. 
While the NPS and FAA are interested 
in evaluating potential solutions to the 
problems at these parks, they are also 
seeking solutions that will make it 
possible to avert problems in the future 
throughout the national park system as 
have developed at these parks. 

Cultural Resources 

Very limited information is available 
on the response of structures to 
subsonic aircraft and helicopters The 



greatest potential risk to historic 
structures and cultural resources in 
units of the national park system is from 
helicopters. The noise characteristics of 
helicopters are such that they tend to 
excite nearby structural elements at 
their resonance frequency, causing low 
frequency vibrations, rattle, and in some 
cases, damage. The sound pressure is 
greatest at structures in the plane of the 
main rotor, such as could be the case for 
a helicopter approaching cliff dwellings. 
When representative cultural resources 
were reviewed for probability of 
damage, most were found to be at some 
risk from commercial air sightseeing 
tours. Mesa Verde (Colorado) and 
Canyonlands National Parks (Utah), 
among others, protest fragile prehistoric 
stone and adobe structures, including 
granaries and cliff dwellings, as well as 
associated cultural materials that are 
susceptible to damage from helicopter- 
induced noise and rotor wash. The 
cultural and spiritual values 
commemorated in units of the national 
park system like San Antonio Missions 
National Historical Parks and the 
battlefields of the Civil War can be 
wholly lost by frequent and intrusive 
commercial air sightseeing tour 
overflights. 

As further examples of areas impacted 
by aircraft overflights. Mount Rushmore 
National Memorial and the Statue of 
Liberty National Monument are cultural 
icons that can be adversely affected in 
significant ways be commercial air tour 
overflights. At the Statue of Liberty, an 
impending aircraft service would take 
off and land helicopters from a floating 
raft less than one-half mile from the 
statue. This service would be added to 
two existing commercial sightseeing 
helicopter operators that account for 115 
flights per day and a service that 
operates four fixed-wing aircraft on air 
tours. Similarly, the experience of 
Mount Rushmore National Memorial for 
the visitors on the ground can be 
irretrievably lost as a consequence of the 
aircraft flights close to memorial. 

Wildlife Effects 

A comprehensive study of the adverse 
effects of commercial air sightseeing 
tours on wildlife in parks has yet to be 
concluded Studies to date indicate that 
aircraft can be associated with stress 
responses on a number of animals, 
including migratory birds. Endangered 
species, like the grizzly bear in Glacier 
National Park, can be harassed by 
commercial air tour operators unaware 
of the potential adverse effects of flying 
too close to them. Other mammals like 
desert bighom sheep, dear, and elk that 
have found refuge in parks can be 
panicked and stressed by low-flying 



aircraft, as well. No studies that evaluate 
long-term effects on wildlife, including 
population level impacts of commercial 
air sightseeing tours, have been 
conducted. As with any potential 
impact associated with activities in 
parks, the NPS policy is to err on the 
side of resource protection until 
conclusive information is available that 
would indicate otherwise. 

Assessing Noise Impacts 

The FAA is working with the NPS to 
define acceptable noise levels as the 
basis for any proposed limitations on 
aircraft overflights. This process 
involves identifying areas with the 
highest levels of noise sensitivity. 
Highly sensitive areas potentially would 
be subject to lower noise limits than 
would apply to other areas with higher 
ambient noise levels, based on resource 
values, types of use, or other factors. 
Depending on local conditions, 
alternative approaches may be 
employed in different areas to achieve 
the same noise goal. 

Current FAA policy and guidelines 
designate the yearly day-night average 
sound level (DNL) as the single noise 
metric for measuring aviation impacts 
on people in and around airports. This 
traditional metric alone may not be 
appropriate for assessing aviation noise 
impacts in parks and wilderness areas. 
Three supplemental metrics other than 
DNL are proven and appear particularly 
suitable for site-specific assessments. 
These are Equivalent Sound Level (L.,,1. 
Sound Exposure Level (SEL) and Time 
Above a dBA Threshold (TA). 
Additionally, defining a change of 5 dB 
as significant at any initial DNL level 
may be appropriate for specifying 
further noise analysis in parks and 
wilderness areas. 

The ongoing NPS studies have 
identified two potential (dose-response 
relationships that also may be 
appropriate for assessing aircraft noise 
impacts. These are "Annoyance vs. 
Percent Time Heard" and "Interference 
with Quiet vs. Percent Time Heard." 
These relationships are preliminary and 
must be subjected to rigorous analysis 
for further determination of their 
potential application. 

Policy Considerations 

In reviewing potential alternatives for 
achieving NPS and FAA purposes, the 
FAA has considered a number of 
measures within its authority under the 
FAAct that would have the potential to 
address the problems identified by the 
NPS. In determining whether a 
particular action would be beneficial for 
this purpose and otherwise feasible, the 
FAA and NPS must take into account a 



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number of legal and policy 
considerations. 

The action, if regulatory, must be 
consistent with Administration 
rulemaking principles as set forth in 
Executive Oder 12866. These 
principles include requirements that 
regulations be drafted in the most cost- 
effective manner to achieve the 
objective; that regulations be based on 
the best reasonably obtainable scientific, 
technical, economic, and other 
information concerning the need for and 
consequences of the action to be taken; 
and that regulations be tailored to 
impose the least burden on society, 
including individuals, businesses, and 
communities, consistent with obtaining 
the regulatory objective. 

The action must have no adverse 
effect on aviation safety. The action 
should have the minimum possible 
adverse effect on the efficiency of air 
navigation, consistent with the 
regulatory objective, and should not 
unduly burden interstate commerce. It 
must also meet NPS requirements for 
protecting resources, assuring that there 
is no impairment, and that there is no 
derogation, to park resources and 
values. 

The action should focus directly on 
the problem rather than indirectly. For 
example, if the issue is the adverse 
impacts of overflights of a unit of the 
national park system, then the agency 
action will address those overflights 
directly, rather than seek to influence 
them through regulation of takeoffs and 
landings at a nearby airport. 

Options for Evaluation 

The FAA and NPS believe that each 
of the following measures may have 
some utility, in certain circumstances, 
as a measure to mitigate the adverse 
effects of commercial air sightseeing 
tour overflights of units of the national 
park system. Inasmuch as some of the 
measures have not been used before, 
neither the FAA nor NPS has concluded 
that such actions would meet the legal 
and policy considerations summarized 
above, and specific comment is 
requested en the benefits, costs, and 
impacts of each. 

Voluntary Measures 

Voluntary, non-regulatory measures 
that mitigate noise impacts would 
impose the minimum burden on 
operators and can be effective. An 
example is the recommended minimum 
altitude of 2.000 feet above ground level 
described in FAA Advisory Circular 91- 
36C. which is honored by most transient 
operators Another option would be 
expansion of the existing Interagency 
Agreement among the FAA, the NPS, 



the Fish and Wildlife Service, and the 
Bureau of Land Management. Through 
that agreement the proponents agree to 
assess severe situations where impact of 
aircraft operations upon human, 
cultural, or natural resources are 
sufficiently serious to warrant 
consideration of site-specific action by 
the FAA to minimize or eliminate the 
causes of such problems. Expansion of 
the Interagency Agreement could 
provide for additional non-regulatory 
actions by the agencies to mitigate 
overflight impacts. The agencies seek 
comments on the relative merits of 
voluntary measures generally, and 
specific suggestions for other voluntary 
measures not currently used by the FAA 
or NPS. 

Grand Canyon Model 

One option is to follow a model 
similar to that in use at Grand Canyon, 
with extensive regulation of airspace, 
routes, and minimum altitudes as 
discussed separately below. Such an 
approach may not adequately consider 
the fact that the total number and 
frequency of flights, and the steady 
growth in numbers of flights, are not 
currently addressed under that 
regulatory framework. 

Prohibition of Flights During Flight-Free 
Time Periods 

A prohibition could be established on 
use of some or all of the airspace above 
parks at certain times; e.g., 1 hour per 
day, 1 day per week, or 2—4 weeks per 
year. The "quiet times" would be 
published well in advance both for air 
tour operator scheduling and for 
planning by park visitors. In terms of 
noise mitigation, non-flying quiet 
periods would present an unusual 
approach to the balance between air 
access and the interest in restoring some 
degree of the natural quiet in Grand 
Canyon National Park. At some cost in 
inconvenience and lost business for air 
tour operators and temporarily reduced 
access to air tours for their passengers, 
the park would enjoy a virtual absence 
of aircraft noise in sensitive areas for 
specific periods. The agencies 
specifically request comment on the 
potential efficacy of these approaches in 
meeting FAA and NPS goals. 

Altitude Restrictions 

SFAR No. 50-2 at Grand Canyon 
currently specifies a minimum altitude 
for flight over the different areas of the 
park as high as 14,500 feet msl. It also 
specifies minimum altitudes for 
operation in the flight corridors between 
the flight-free zones. Different altitudes 
are specified for transient general 
aviation operations and for air tour 



operators, to separate high-frequency 
tour flights from one-time transient 
flights. Different altitudes are also 
specified for fixed-wing aircraft and 
helicopter tour flights, for safety and - 
efficiency reasons. The tour operation 
altitudes are at canyon rim level or 
above (although some are slightly below 
the minimum altitude requested by NPS 
as "rim level" in 1987). A relatively 
high minimum altitude in a particular 
area limits access to the airspace over 
that area by many general aviation 
aircraft because of performance 
limitations. Generally, noise mitigation 
is achieved through higher minimum 
altitudes because the greater the slant- 
range distance from an aircraft to a point 
on the surface, the lower the sound level 
on the surface from aircraft noise. 
However, this mitigation can be offset or 
reversed based on attenuation factors 
such as hills, heavily wooded areas, and 
"soft ground" terrain. 

Flight Free Zones/Flight Corridors 

SFAR No. 50-2 at Grand Canyon now 
describes specific "flight-free" zones to 
an altitude of 14,500 feet msl above the 
park. The remaining airspace is defined 
as corridors for operations over the park 
by both general aviation and 
commercial air tour operators. Impact 
mitigation is achieved through ' 
specifying corridors for flight over the 
park that assure there are no overflights 
of large areas of the park below the 
current minimum altitude of 14,500 feet 
msl. The current corridors and flight- 
free zones could be amended to address 
concerns about effects on particular 
areas of the park 

Restrictions on Noise Through 
Allocation of Aircraft Noise 
Equivalencies 

A noise budget is a mechanism for 
limiting total aircraft noise impact on 
the park by assigning each air tour 
operator an individual limit on noise 
impact. This would allow Individual air 
tour operators the flexibility to decide 
what combination of equipment and 
flight frequency they will use to attain 
the target noise level. The noise budget 
would apply only to air tour sightseeing 
operators and not to transient general 
aviation operations. The noise budget 
concept assumes that the FAA and NPS 
could determine (1) the acceptable 
amount of aircraft noise exposure on the 
park surface, and (2) the number of 
aircraft operations under various mixes 
of aircraft types that could operate 
within the iotal noise budget. 

While complex to develop and 
administer, the noise budget could 
achieve noise mitigation through 
directly addressing the issue of noise 



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12745 



impact but would not address the 
impacts other than noise Once the 
"budget" is established based on target 
noise levels in various areas of the park, 
air tour operators would have 
substantial flexibility to adjust their 
business operations without exceeding 
those levels. The noise budget could act 
as a practical limit on the amount of 
aviation activity, but would not impose 
limits on the number of operations. A 
noise budget would also represent an 
incentive Tor operators to acquire 
relatively quiet aircraft to avoid a 
penalty on the number of operations 
that could be conducted within each 
operator's target noise level. 

Individual Allocations under a noise 
budget could be established by 
designating maximum noise levels for 
each operator. This could be done by 
"grandfathering" the current noise 
contribution by each air tour operator, 
or by some other administrative means. 

Incentive* To Encourage Use of Quiet 
Aircraft 

Air tour operators could be 
encouraged to use relatively quiet 
aircraft on park overflights. For 
example, a flight corridor with a good 
scenic view of the canyon could be 
limited to aircraft meeting certain noise 
emission standards. An air tour operator 
could find it advantageous to convert its 
entire fleet to such quiet aircraft to 
incorporate that corridor in its tours. 
While there is no Federal requirement 
for aircraft to be manufactured to 
produce less noise than Stage 3 
standards, some aircraft appropriate for 
air tour operations are quieter than 
Stage 3. Increased use of such aircraft in 
air tours would achieve noise mitigation 
through reducing noise levels on the 
surface of the park, although this option 
does not address issues other than 
noise. 

Q u es ti ons 

The MPS and FAA also solicit 
comments on several questions related 
to air tour sightseeing operations in and 
adjacent to units of the national park 
system. 

Policy 

1. Should commercial sightseeing 
flights be prohibited over certain 
national parks? If so. what criteria 
should be used in determining which 
parks should not have such tours? 



2. Should action pertaining to aircraft 
overflights in national parks be 
considered only for air tour/9ightseeing 
operations? What circumstances would 
include other categories of overflights? 

3. What factors should be considered 
by NFS and FAA in evaluating 
recommendations for addressing aircraft 
overflight issues? 

Technical 

1. Is the use of quiet technology 
aircraft a viable alternative for reducing 
noise from commercial air tour/ 
sightseeing operations in national 
parks? 

2. Should all commercial air tour/ 
iightseeing operations be conducted 
under air carrier rules of FAR pan 135 
and/or 121? 

3. Should air carrier operators be 
required to have special operations 
specifications for conducting 
sightseeing flights? 

4. Should there be special airspace 
rules for identified units of the national 
park system? 

5. Should the measures developed for 
Grand Canyon and Hawaii become 
models for more general use at parks 
with actual or potential overflight 
Impacts? 

Request for Comments 

The FAA and NPS solicit comments 
and information from all segments of 
the public interested in aviation and 
national parks and their relationship. 
The primary focus of this advance 
notice is commercial air sightseeing 
tours, rather than military or general 
aviation operations. It is anticipated that 
any regulations eventually developed 
would be general in nature and 
applicable to the entire national park 
system. It is not the intent of the NPS 
or FAA to develop regulations specific 
to any one park at this time. However, 
examples of aviation activities observed 
in one park may be used to support an 
opinion on overall aviation management 
issues. 

All comments received by FAA and 
NPS at the addresses and by the dates 
listed above will be reviewed and 
utilized in any development of 
proposed regulations. Comments 
received pursuant to this Advance 
Notice of Proposed Rulemaking will be 
analyzed and discussed in the preamble 
to the Proposed Rule. Any proposed 



rulemaking will also be made available 
for public review and comment. 

Regulatory Process Matters 

Economic Impact 

The FAA and NPS are unable to 
determine at this point the likely costs 
of imposing regulations affecting 
overflights of national parks or the 
annual effect on the economy. 
Following a review of the comments 
submitted to this ANPRM. the FAA and 
NPS will determine what regulatory 
requirements will be proposed, if any. 
and will review the potential costs and 
benefits, as required bv Executive Order 
12866. 

S/gnj/iconce 

This anticipated rulemaking is not a 
"significant regulatory action" as 
defined in Executive Order 12866. The 
FAA has determined that the ANPRM is 
not significant under the Regulatory 
Policies and Procedures of the 
Department of Transportation (44 FR 
11034. February 2. 1979). 

Other Regulatory Matters 

At this preliminary stage it is not yet 
possible to determine whether there will 
be a significant economic impact on a 
number of small entities or what the 
paperwork burden might be These 
regulatory matters will be addressed at 
the time of publication of any NPRM on 
this subject. 

List of Subjects 

36 CFR Ports J through 7 

Grand Canyon National Park. 
Haleakala National Park. Hawaii 
Volcanoes National Park. 

14 CFR Parts 91 and 135 

Aircraft. Airmen. Airports, Air taxis. 
Air traffic control. Aviation safety, 
Noise control. 

Issued In Washington. DC on March 11. 
1994. 

Barry L. Valentine, 

Assistant Administrator for Policy. Planning. 
fr International Aviation. 

George T. Frunpton, Jr.. 

Assistant Secretary of Interior. Fish and 

Wildlife and Parks. 

|FR Doc 94-6216 Filed 3-14-94; 12:28 pm| 

BILLMO COOC <9iH)-M 



304 



APPENDIX E 



AIR NATIONAL GUARD 



Policy on Overflights of Designated Wilderness and 
Wild and Scenic Rivers 



305 



APPENDIXES: Appendix E 



Policy on Air National Guard Overflights of Designated Wilderness and Wild 
and Scenic Sites 

INTRODUCTION 

The Air National Guard recognizes the intent of Congress in establishing Wilderness and the Wild and Scenic 
River Systems, and the benefits of recreation and other activities to be derived from these areas. As defined in the 
lain, wilderness is an area where the earth and its community of life are untrammeled by people, and inhere people 
are visitors. Despite this general operating framework, the Congress has authorized many activities, e.g. recreation, 
commercial outfitting, guide services, and livestock grazing. Many other activities are also permitted, including 
administrative structures and installations, development of privately owned minerals, fire control, and insect and 
disease control. In some cases the use of airstrips and motorboats are also authorized. Commercial and military 
aircraft overflights of Wilderness and Wild and Scenic Rivers are not excluded under the legislation. The ANG has 
potential to impact these areas; therefore this policy is put forth with the, recognition of the importance of these 
national assets. 

POLICY STATEMENT 

The following assumptions and facts affect the ANG position on overflights: 

■ There is an increasing awareness and interest on the part of the public regarding management of 
wilderness. This is evidenced by a recent GAO report on wilderness preservation, an MOU between DOD 
and the U.S. Forest Service, the Nevada Wilderness Act, and the National Park Overflights Act. 

■ The Wilderness System constitutes about 91 million acres, 34.2 million of which is located in 42 of the 
contiguous states and accounts for one (1) out of every six (6) acres of Forest Service land. 

■ Additional land will be added to both the Wilderness System and the Wild and Scenic Rivers System. 

■ Legal action has been taken against the ANG at the Boundary Waters Canoe Area Wilderness regarding 
overflights. 

■ Wilderness and Wild and Scenic Rivers were designated for several uses not just recreational. The 
establishment of these areas will allow natural processes to operate freely within wilderness. 

■ Overflights, both commercial and military, were taking place prior to designation of Wilderness and Wild 
and Scenic Rivers. 

■ The ANG is concerned about its overflight activity on these areas, and the potential impact on visitors. 

■ The only FAA policy on overflight activity of these areas is a 2000 ft AGL flight advisory. 

■ The ANG requires various types of airspace in which to safely conduct its operations and therefore prefers 
to use lighdy populated areas such as those that may contain wilderness. Many of the existing ANG MOAs 
and MTRs are located over existing Wilderness and Wild and Scenic River corridors. 

Given this framework, it is ANG policy: 

■ To comply with all FAA regulations and applicable federal legislation. 



306 



Policy on Air National Guard Overflights of Designated V/ildemess and Wild and Scenic Sites 



To not plan any ANG ground activity on designated Wilderness or Wild or Scenic River areas, to include 
air drops and troop activity. 

Newly proposed airspace and modification of existing airspace will be planned to avoid these areas unless 
mission constraints dictate otherwise. 

The Operational and Resources Study (OARS) shall identify the rationale, and provide justification for 
Wilderness and Wild and Scenic River overflights. 

Wilderness will be overflown at 2000 ft AGL or higher whenever possible to comply with the intent of the 
FAA advisory on overflights. 

There will not be any type of ANG structure, either temporary or permanent, within these areas, e.g. radar 
sites or communication sites. 

The units will coordinate with the appropriate manager of a Wilderness or Wild and Scenic River in terms 
of solving specific problems associated with ANG use of that airspace. This may include defining prohibited 
areas, altitude above terrain reservations, and areas of partial or seasonal closure. 

Newly proposed overflight activity will go through the appropriate Environmental Impact Analysis Process 
(EIAP) to identify environmental impacts, and to insure the proper coordination with interested agencies. 



CONCLUSION 

The ANG can be viewed as a visitor, in the air, to these areas. The impact, although of concern to a wilderness user 
because of its potential to impact their solitude, is of short duration, infrequent, and often not visible. Various 
environmental assessments completed for airspace have indicated that impacts on wildlife and air quality are 
minimal. These impacts will become even less of a factor as the ANG continues to convert its forces to quieter and 
cleaner aircraft. The ANG mission requires the use of loin altitude airspace in remote areas to avoid more densely 
populated areas, and to operate in a safe manner. In light of the vastness and distribution of the Wilderness and 
Wild and Scenic Rivers systems it is inevitable that overflights be conducted. ANG overflights will not preclude 
other uses for these areas, and in most cases will provide less of an impact on the system than on ground 
recreational use. Natural processes can continue to operate freely, as they have in the past. 

Regardless, it will be ANG policy to plan its airspace to avoid these areas as much as possible. Where it is not 
possible, this criteria will be used. The ANG will continue to recognize its role in preserving our nation's pristine 
areas, and do what it can to enhance them. 



307 



APPENDIX F 



Interagency Airspace/Natural Resource Coordination Group (IANRCG) 

Statement of Principles for a Partnership For Action to Protect, Restore and Maintain the Nation's 
Airspace and Federally Protected Land Resources 

Statement of Principle 

To engage in a partnership to identify issues and facilitate cooperative problem resolution concerning use of 
airspace over federally protected lands. 

Background 

The Departments of Agriculture (Forest Service), Defense (DOD) and Interior (DOI) have legal responsibilities to 
manage or use important land-based resources to meet national interests, mandates, and responsibilities. These 
agencies also use airspace which the Federal Aviation Administration (FAA) manages. Currendy and for the 
foreseeable future, the Department of Defense will require access to suitable airspace in which aircrews can train 
realistically to meet national security objectives. The Departments of Agriculture and Interior also require access to 
airspace overlying the lands they manage to provide mandated natural resource protection. 

Much of the FAA-approved airspace for DOD flight training, and many non-DOD training and operational flights, 
traverse federally protected lands. These federally protected lands include units of the National Park System, 
National Wilderness Preservation System, National Wildlife Refuge System, National Forest System, and National 
Wild and Scenic River Systems, and national refuge areas. Collectively, the National Park Service, Forest Service, 
Bureau of Land Management, and the Fish and Wildlife Service manage over 500 million acres of public land. In 
addition, Indian Affairs protects trust resources associated with 53 million acres of non-public land for the use and 
benefit of Indian beneficiaries. Additionally, the DoD has stewardship responsibility for 25 million acres of land. 
While each agency's responsibility varies to some degree, each agency has legal responsibility including the 



309 



APPENDIXES: Appendix F 



preservation of wilderness areas, protection of natural and cultural resources, and promotion of public enjoyment 
and use of these resources. 

Management and administration of federally managed lands lor these purposes may encounter 
competing/conflicting interests. To ensure the public's interests are served equitably, representatives from each 
agency will meet as often as necessary to resolve issues to ensure national interests, mandates, and aviation 
operational, training and safety objectives are being met. Further, this interagency group, known as the Interagency 
Airspace/Natural Resources Coordination Group (IANRCG or Coordination Group), will engage in a cooperative 
effort to identify issues, recommend procedures, and facilitate a process to resolve these issues. 

Statutory Basis 

The Coordination Group will operate within existing authorities and serve to identify and fulfill the many Federal 
statutes that affect air and land resources. Some of these statutes include the Wilderness Act, Wild and Scenic 
Rivers Act, Federal Land Policy and Management Act, Endangered Species Act, National Environmental Policy Act, 
the Federal Aviation Act of 1958, and the American Indian Religious Freedom Act. The Coordination Group will 
make recommendations to their principal agencies but it has no enforcement or regulatory authority. 

Purpose 

The purpose of the Coordination Group is to assist in protecting, conserving, and restoring the Nation's airspace 
and federally protected land areas through existing Federal capabilities and authorities; establish lines of 
communication to identify and facilitate problem/issue resolution related to airspace and land use; establish a 
cooperative stewardship of air and land resources by working in partnership with other Federal agencies; enhance 
aviation safety and operational deconfliction; integrate Federal actions and programs with state, local, and 
non-governmental efforts; and to provide a framework for action that effectively focuses agency expertise and 
resources on joindy identified problems to facilitate demonstrable environmental and programmatic results that 
may serve as models for effective management of air and land resources. The Coordination Group will work to 
identify and facilitate potential issue and conflict resolution at the preliminary stages of planning and develop 
recommendations for joint military training and information sharing opportunities. 

General Scope 

The Coordination Group provides a forum for interagency discussion, integrated planning, collaborative dispute 
resolution, and facilitation of local and regional issues concerning die use of the nation's federally protected land 
resources and airspace. Initial efforts of the Coordination Group will focus on issues and conflicts among airspace 
and land managers which have been identified. 

Coordination Group membership may include representatives from the Departments of the Air Force, Army, Navy 
(including the Marine Corps), their respective reserve components, Federal Aviation Administration, Bureau of 
Land Management, Department of the Interior, Assistant Secretary -Indian Affairs, Fish and Wildlife Service, 
National Park Service, Forest Service, and other interested Federal agencies or organizations which have 
jurisdiction, mandates, responsibilities, or interests in federally protected lands and airspace. 



310 



Interagency Airspace/Natural Resource Coordination Group (7ANRCG) 



Responsibilities 

The coordination group will: 

■ Meet regularly to identify conflicts early in the airspace and land use planning process and facilitate 
resolving conflicts at the lowest practical level. 

■ Foster a continuous dialogue between representatives and contribute to a cooperative environment in 
which conflicts can be avoided or, failing that, facilitate resolving conflicts so as to achieve mutual goals. 

■ Provide an effective forum for operational feedback and information sharing. 

■ Provide a stewardship role toward all airspace for military use and all federally designated protected land, as 
tasked within the control of the Departments of Agriculture (Forest Service), Defense and Interior. 

■ Adopt a proactive role with respect to lands, wildlife, waterways and airspace, and protect, as much as 
possible, the welfare of the environment and sensitivities of concerned citizens. 

■ Establish sub-committees as necessary to staff issues. 

■ Institute management procedures to serve as the basis for future interagency airspace and land planning 
coordination. 

■ Whenever feasible, take intra-agency action to resolve problems identified by other agencies. 

■ Identify ways to conserve, revise, and/or delete, monitor, and otherwise protect airspace and land assets to 
meet future military training needs and be responsive to other public interests.. 

■ Strive to increase aviation safety and provide operational deconfliction 

■ Identify opportunities for training, education, and research needs for land managers and airspace planners 

Reports 

The Coordination Group will document the recommendations and proceedings of each meeting and send copies 
to each agency representative as soon as practical following the meeting. The Coordination Group may prepare a 
comprehensive annual report that documents the management actions accomplished and evaluates the 
effectiveness of programmatic decisions and recommendations and other reports as appropriate and mutually 
agreed to. 



311 



APPENDIX G 



Deputy Under Secretary of Defense (Environmental Security) 
Response to the Senate Armed Services Committee Report 103-1 12 



313 



APPENDIXES: Appendix G 




OFFICE OF THE UNDER SECRETARY OF DEFENSE 

SOOO DEFENSE PENTAGON 
WASHINGTON DC 20301-3000 




ACOUtHTlOW AMO 
TCCMNOUMV 



07- 4CT ffil 

Honorable Sam Nunn qqj ~ 

Chairman, /Committee on Armed Services ° 

United States Senate 
Washington, DC 20510-6050 

Dear Mr. Chairman: 

This letter is in response to the Senate Armed Services Committee 
Report 103-112, National Defense Authorisation Act of FY 1994, which 
directs the Secretaries of Defense and Interior to provide a report on 
what procedures have been developed to achieve their mutual goals of 
training and stewardship. 

We have prepared the enclosed interim report in conjunction with 
the Department of the Interior. It reflects agreement between our two 
agencies that a recently established informal coordination group could 
be the model for a mechanism to resolve disputes, and such a group may 
be incorporated into procedures we are presently developing to achieve 
our mutual goals. We have begun an expanded interagency dialogue that 
has already resulted in the drafting of a Memorandum of Understanding, 
through which DoD and Dol would communicate, cooperate, and coordinate 
on national defense and natural resources concerns. When we complete 
our development of the procedure directed by the SASC, we will provide 
a final report that describes it in detail. 



Very truly yours, 




U)(Ll 



aerri W. Goodman 
Deputy Under Secretary of Defense 
(Environmental Security) 



Enclosure 

cc: 

Honorable Strom Thurmond 

Ranking Republican 



Environmental Security \M Defending Our Future 



314 



Deputy Under Secretary of Defense (Environmental Security) 



REPORT TO THE COMMITTEE ON ARMED SERVICES 
UNITED STATES SENATE 



The Department of Defense mission is to maintain national security by 
maintaining combat readiness. Readiness depends on well equipped and 
well trained fighting forces. The requirement to train the forces is 
determined both by the weapons and tactics expected to be employed in 
battle, and by the conditions and terrain of the battlefield. In our 
training, we emphasize realism and results, and to find these we have 
had to move some of our activities to the national forests and public 
lands managed by the Departments of Agriculture and Interior. If the 
committee is interested, we have a videotape describing this training 
that we would like to share with you, at your request. 

Our agencies know that the Congress, the general public, and national 
and local natural resource and wildlife advocacy groups are concerned 
with military ground operations and overflights, because they believe 
we are disturbing the ecology of these forests and lands. We realize 
that we have a common interest in such areas, and we are committed to 
cooperating in an effort to conserve or enhance our natural heritage, 
and to assure a satisfactory national defense. Over the past several 
months, our agencies, as well as the Department of Transportation and 
the Federal Aviation Administration, have participated in discussions 
of several legislative initiatives affecting overflights and refuges. 
From this interchange, an informal group now known as the Interagency 
Airspace and Natural Resources Coordination Group (IANRCG) evolved. 

This newly formed group met for the first time in late January, 1994, 
at Andrews Air Force Base, Maryland at the invitation of Air National 
Guard personnel who hosted and facilitated the meeting. The group is 
composed of military airspace users and Federal land managers, and it 
met a second time in May to continue the January dialogue and address 
airspace and land issues. 

The following agencies were represented at the May meeting: 

• Department of Defense 

- Deputy Under Secretary of Defense (Environmental Security) 

- Department of Army 

- Department of Navy 

- Department of Air Force 

- Headquarters U.S. Marine Corps 

- Army National Guard 

- Air National Guard 

- Air Force Reserve 



315 



APPENDIXES: Appendix G 



• Department of Agriculture 

- U.S. Forest Service 

• Department of Interior 

- Assistant Secretary - Indian Affairs 

- Bureau of Land Management 

- National Park Service 

- Office of Aircraft Services 

- U.S. Fish and Wildlife Service 

The group discussed the Senate Armed Services Committee (SASC) Report 
#103-112, National Defense Authorization Act for FY 1994. "It directs 
the Secretary of Defense and the Secretary of Interior to establish a 
procedure, including a mechanism for dispute resolution, by which DoD 
and Dol can achieve their mutual goals of training and stewardship. 

Attendees agreed that the informal group, or IANRCG, could facilitate 
establishment of the procedure sought by the Committee, in that staff 
and mid-level managers of the interested agencies have recognized and 
accepted it. And, between the January and May meetings of the group, 
DoD and Dol representatives were successful in resolving longstanding 
problems the agencies had identified in January. This process may be 
a model for the dispute resolution mechanism desired by the SASC; but 
it should only complement existing agency organizations and processes 
through which our agencies presently accommodate national defense and 
natural resources needs. 

Encouraged by the successful resolution of these problems, the IANRCG 
formed five subcommittees to consider and propose solutions to common 
problem areas, on a continuing basis: 

• Coordination and Procedure 

• Education and Awareness 

• Environmental Effects 

• NEPA Planning and Compliance' 

• Operations and Safety 

Although DoD already has its own Policy Board on Federal Aviation for 
dealing with airspace issues, it is also considering establishment of 
an interagency group that would recommend policy on both airspace and 
natural resources, the Airspace and Natural Resources Steering Group. 
The new group should meet once or twice a year, and members may be ex 
officio Assistant or Deputy Under Secretaries of Federal agencies, or 
leaders of selected natural resources and wildlife advocacy groups. 



316 



LIST OF REFERENCES 



Ajzen, I. and M. Fishbein 

1980 Understanding Attitudes and Predicting Social Behavior, Prentice- Hall, Inc., Englewood Cliffs, NJ. 

Andersen, D.E., Rongstad, O.J. and W.R. Mytton 

1 989 Response of nesting red-tailed hawks to helicopter overflights. Condor 9 1 :296-299. 

Andersen, R. 

197 1 Effect of human disturbance on Dall sheep. Alaska Cooperative Wildlife Unit Quarterly Report 22:23-27. 

Anderson, G.S. and R.D. Horonjeff 

1992 "Effect of Aircraft Altitude Upon Sound Levels at the Ground," HMMH Report No. 290940.02, NPOA 
Report No. 91-4. 

Anderson, G.S., et al 

1993 "Dose-Response Relationships Derived from Data Collected at Grand Canyon, Haleakala and Hawaii 
Volcanoes National Parks," HMMH Report No. 290940.14, NPOA Report No. 93-6. 

Austin, O.L., Jr., Robertson, W.B., Jr., and G.E. Woolfenden 

1970 Mass hatching failure in Dry Tortugas Sooty terns (Sterna fuscata). pp.627 in: K.H. Vous, ed. Proceedings, 
1 5th International Ornithological Congress, The Hague, Netherlands. 

Ballard, W. 

1975 Mountain goat survey technique. Alaska Fed. Aid. Wildl. Rest. Rept., Project W-17-7, 12.2. Alaska Dept. 
Fish and Game, Juneau. 2 1 pp. 

Baumgartner, R.M. and CD. McDonald 

1994 "Grand Canyon Visitor Survey," HMMH Report No. 290940.19, NPOA Report No. 93-5. 



317 



LIST OF REFERENCES 



Belanger, L. and J. Bedard 

198% Responses of staging greater snow geese to human disturbance. Journal of Wildlife Management 

53:713-719. 
1 9896 Energetic cost of man-induced disturbance to staging snow geese. Journal of Wildlife Management 

54:36-41. 

Bennett, R. and C. Cox 

1994 "Grand Canyon Comparative Sound Study." 

Berger, J., Daneke, D., Johnson, J. and S. Berwick 

1983 Pronghorn foraging economy and predator avoidance in a desert ecosystem: Implications for the 
conservation of large mammalian herbivores. Biological Conservation 25:193-208. 

Bergerud, A. T. 

1 963 Aerial winter census of caribou. Journal of Wildlife Management 27:430-449. 

1978 Caribou, pp.83- 101 in: J.L. Schmidt and D.L. Gilbert, eds. Big Game of North America: Ecology and 
Management. Wildlife Management Institute, Stackpole Books, Harrisburg, PA„ 

Black, B.B., Collopy, M.W., Percival, H.F., Tiller, A.A. and P.G. Bohall 

1984 Effect of low-level military training flights on wading bird colonies in Florida. Florida Cooperative Fish 
and Wildlife Research Unit, School of Forestry and Resource Conservation, University of Florida, 
Gainesville. Technical Report No. 7. 190 pp. 

Bleich, V.C., Bowyer, R.T., Pauli, A.M., Vernoy, R.L. and R.W. Anthes 

1990 Responses of mountain sheep to helicopter surveys. California Fish and Game 76:197-204. 

Bondello, M. 

1 976 The effects of high-intensity motorcycle sounds on the acoustical sensitivity of the desert iguana, 
Dipsosaurus dorsalis. MA. thesis, California State University, Fullerton. 37 pp. 

Bondello, M.C. and B.H. Brattstrom 

1979 The experimental effects of off-road vehicle sounds on three species of desert invertebrates. Report to the 
Bureau of Land Management. 61 pp. 

Borg, E. 

1979 Physiological aspects of the effects of sound on man and animals. Acta Otolaryngologia. Supplement 
360:80-85. 

Braid, R.B. 

1 992 Incorporation of public participation in environmental analyses of low-altitude flying operations. The 
Environmental Professional 14:60-69. 

Brown, A.L. 

1990 Measuring the effect of aircraft noise on sea birds. Environment International 16:587-592. 

Brown, D.A. 

1990 Integrating environmental ethics with science and law. The Environmental Professional 12:344-350. 



318 



Lisf of References 



Bunnell, F.L., Dunbar, D., Koza, L. and G. Ryder 

1981 Effects of disturbance on the productivity and numbers of white pelicans in British Colombia — 
observations and models. Colonial Waterbirds 4:2- 11. 

Burger, J. 

1 98 1 Behavioral responses of herring gulls (lams argentatus) to aircraft noise. Environmental Pollution (Series 
A) 24:177-184. 

Burkholder, B. 

1959 Movements and behavior of awolf pack in Alaska. Journal of Wildlife Management 17:10-13. 

Calef, G.W. and G.M. Lortie 

1973 Observations of the Porcupine caribou herd, 1972. Towards an environmental impact assessment of the 

portion of the Mackenzie gas pipeline from Alaska to Alberta. Interim Report No. 3, Appendix 1, 

Environmental Protection Board, Winnipeg. 

Calef, G.W., DeBock, E.A. and G.M. Lortie 

1 976 The reaction of barren-ground caribou to aircraft. Arctic 29:20 1 -2 1 2. 

Canter, L.W., Robertson, J.M. and R.M. Westcott 

1991 Identification and evaluation of biological impact mitigation measures. Journal of Environmental 
Management 33:35-50. 

Carrier, W.D. and W.E. Melquist 

1976 The use of a rotor-winged aircraft in conducting nesting surveys of ospreys in northern Idaho. Raptor 
Research 10:77-83. 

Chadwick, D. 

1973 Mountain goat ecology: Logging relationships in Bunker Creek drainage of western Montana. Montana 

Federal Aid Wildlife Restoration Project Report, Project W-120-R-3. 4. Montana Fish and Game 

Department, Bozeman. 262 pp. 

Chesser, R.K., Caldwell, RS. and M.J. Harvey 

1975 Effects of noise on feral populations of Mus musculus. Physiological Zoology 48:323-325. 

Christiansen, M.L. and K.S. Yonge 

1979 Research update: Bird deterrent and dispersal systems. Syncrude Canada, Ltd. Professional Paper 
1981-3. 13 pp. 

Cook, J.G. and S.H. Anderson 

1 990 Use of helicopters for surveys of nesting red-shouldered hawks. Prairie Naturalist 22:49-53. 

Council on Environmental Quality 

1978 NEPA Regulations. Federal Register 43(230) 29 Nov. 55978 - 56007. 

Craig, T.H. and E.H. Craig 

1984 Results of a helicopter survey of cliff nesting raptors in a deep canyon in southern Idaho. Raptor Research 
18:20-25. 



319 



LIST OF REFERENCES 



Davis, R.A. and A.N. Wisely 

1 974 Normal behavior of snow geese on the Yukon- Alaska North Slope and the effects of aircraft- induced 
disturbance on this behavior, September 1973. Arctic Gas Biological Report Series 27:1-85. 

Denenberg, V.H. and K.M. Rosenberg 

1967 Non-genetic transmission of information. Nature 2 16:549-550. 

Ditton, R., Graefe, A. and R. Fedler 

198 1 "Recreational Satisfaction at Buffalo National River: Some Measurement Concerns," Some Recent Products 
of River Recreation Research, USDA Forest Service General Technical Report, NC-63. 

Dorfman, P. 

1 979 "Measurement and Meaning of Recreation Satisfaction: A Case Study in Camping," Environment and 
Behavior, 1 1, p. 483-510. 

Dunholter, P.H., Mestre, V.E., Harris, RA. and L.F. Cohn 

1989 "Methodology for the Measurement and Analysis of Aircraft Sound Levels within National Parks," Mestre 
Greve Associates, MGA Technical Report # 89-P07. 

Dunnett, G.M. 

1977 Observations on the effects of low-flying aircraft at seabird colonies on the coast of Aberdeenshire, 
Scodand. Biological Conservation 12:55-63. 

Edwards, R.G., Broderson, A.B., Barbour, R.W., McCoy, D.F. and C.W. Johnson 

1979 Assessment of the environmental compatibility of differing helicopter noise certification standards. 
Report to US Department of Transportation, FAA. 58 pp. 

Ellis, D.H., Ellis,^C. and D. Mindell 

1991 Raptor responses to low-level jet aircraft and sonic booms. Environmental Pollution 74:53-83. 

Ericson, C.A. 

1972 Some preliminary observations on the acoustic behaviour of semi-domestic reindeer (Rangifer tarandus 

tarandus) with emphasis on intraspecific communication and the mother-calf relationship. M.S. thesis, 

University of Alaska, Fairbanks. 121 pp. 

Fancy, S.G. 

1 982 Reaction of bison to aerial surveys in interior Alaska. Canadian Field Naturalist 96:9 1 . 

Federal Aviation Administration 

1 988 Report to Congress, Results of Surveillance of Aircraft Flights Over the Boundary Waters Canoe Area Wilderness. 

Feist, J., McCrory, W. and H. Russell 

1974 Distribution of Dall sheep in the Mount Goodenough area, Northwest Territories, in: K.H. McCourt and 
L.P. Horstman, eds. Studies of Large Mammal Populations in Northern Alaska, Yukon, and Northwest 
Territories, 1973. Renewable Resources Consulting Services, Ltd., Canadian Arctic Gas Study Biological 
Report No. 22. 

Fidell, Sanford, et al. 

1994 "Evaluation of the Effectiveness of SFAR 50-2 in Restoring Natural Quiet to Grand Canyon National 
Park," BBN Systems and Technologies, Report No. 7 197, NPOA Report No. (Unassigned). 



320 



List of References 



Fishbein, M. and I. Ajzen 

1975 Belief, Attitude, Intention and Behavior: An Introduction to Theory and Research, Addison- Wesley, Reading, MA. 

Fjeld, P.E., Gabrielsen, G.W. and J.B. Orbek 

1988 Noise from helicopters and its effect on a colony of Brunnich's guillemots (Uria lomria) on Svalbard. in: 
P.E. Presterud and N.A. Ortisland, eds. Norsk Polariustitutt, Rapportserie No. 41. pp. 1 16-153. 

Fletcher, J. L. 

1980 Effects of noise on wildlife: A review of relevant literature. 1971-1978. pp. 61 1-620 in: J.V. Tobias, G. 

Jansen, and W.D. Ward, eds. Proceedings, Third International Congress on Noise as a Public Health Problem. Am. 

Speech-Language-Hearing Assoc, Rockville, MD, ASHA Rep. 10. 

Fletcher, J. 

1990 Review of noise and terrestrial species: 1983-1988. pp. 181-188 in: B. Berglund and T. Lindvall, eds. 

Noise as a Public Health Problem Vol. 5: New Advances in Noise Research Part II. Swedish Council for Building 

Research, Stockholm. 

Frazier, A.R. 

1972 Noise survey, F- 105 overflights, Wichita Mountains Wildlife Refuge and vicinity, Fort Sill, Oklahoma. 
U.S. Dept. Commerce, NTIS, Springfield, VA. 62 pp. 

Geist, V., Alberta Society of Professional Biologists. 

[Letter to Dr. R. DiGrazia, North American Foundation for Wild Sheep, re: Review of the Draft 
Environmental Impact Assessment, Idaho Air National Guard Training Range]. January 6, 1994 . 

Geist, V. 

1 97 1 A behavioral approach to the management of ungulates, in: E. Duffey and A.S. Watt, eds. The Scientific 

Management of Animal and Plant Communities for Conservation. Oxford, Blackwell Scientific Publications. 
1978 Behavior. Chapter 19, pp. 283-296 in: L. L. Schmidt and D. L. Gilbert, eds. Big Game of North America. 

Stackpole Books, Harrisburgh. 

Gladdys, P.A. 

1983 Staff, Cross Creek National Wildlife Refuge. Memorandum, US Fish and Wildlife Service, to SAC, LE 
District 4, Adanta, GA. 

Gladwin, D.N., Asherin, D.A. and K.M. Manci 

1987 Effects of aircralt noise and sonic booms on fish and wildlife: Results of a survey of U.S. Fish and Wildlife 

Service endangered species and ecological services field offices, refuges, hatcheries, and research centers. 

NERC-88/30. USFWS, National Ecology Research Center, Fort Collins, CO. 24 pp. 

Gollop, M.A., Davis, R.A., Prevett, J.P. and B.E. Felske 

1972 Disturbance studies of terrestrial breeding bird populations: Firth River, Yukon Territory, June, 1972. pp. 
97- 1 52 in: W.W.H. Gunn and J. A. Livingston, eds. Arctic Gas Biological Report Series Volume 14. 

Gollop, M.A., Black, J.E., Felske, B.E. and R.A. Davis. 

1 974a. Disturbance studies of breeding black brandt, common eiders, glaucous gulls, and Arctic terns at Nunaluk 

Spit and Philips Bay, Yukon Territory, July, 1972. pp. 1 53-202 in: W.W.H. Gunn and J. A. Livingston, 

eds. Arctic Gas Biological Report Series Volume 14. 



321 



LIST OF REFERENCES 



Gollop, M.A., Goldsberry, J.R. and R.A. Davis. 

1914b. Aircraft disturbance to molting sea ducks, Herschel Island, Yukon Territory, August, 1972. pp. 202-232 
in: W.W.H. Gunn and J.A. Livingston, eds. Arctic Gas Biological Report Series Volume 14. 

Greider, Thomas 

1993 "Aircraft Noise and the Practice of Indian Medicine: The Symbolic Transformation of the Environment," 
Human Organization 52(1): 76-82. 

Gunn, A., Miller, F.L., Glaholt, R. and K. Jingfors 

1985 Behavioral responses of barren-ground caribou cows and calves to helicopters on the Beverly herd calving 

ground, Northwest Territories, pp. 10- 14 in: A.M. Martell and D.E. Ressell, eds. Caribou and human actmty. 

Proceedings, 1st North American Caribou Workshop, Whitehorse, Yukon 1983. 

Harding, L.E. and J.A. Nagy 

1976 Responses of grizzly bears to hydrocarbon exploration on Richards Island, Northwest Territories, Canada. 
Bear Symposium, Kalispell, Montana. 

Harrington, F.H. and A.M. Veitch 

1991 Short-term impacts of low-level jet fighter training on caribou in Labrador. Arctic 44:3 18-327. 

1992 Calving success of woodland caribou exposed to low-level jet fighter overflights. Arctic 45:213-218. 

Harrison, J.M. 

1984 The functional analysis of auditory discrimination. Journal of Acousical Society of America 75:1845-1854. 

Hanson, C.E. 

1991 "Aircraft Noise Effects on Cultural Resources: Review of Technical Literature", HMMH Report No. 
290940.04-1, NPOA Report No. 91-3. 

Hammit, W., McDonald, C. and M. Peterson 

1 990 "Determinants of Multiple Satisfactions for Deer Hunting," Wildlife Society Bulletin, 1 8, pp 33 1-337. 

HBRS, Inc. 

1994 "Air Tour Passengers Survey," HMMH Report No. 290940. 1 5, NPOA Report No. 94- 1 . 

1994 "Survey of National Park Service Managers Related to Aircraft Overflying National Parks," HMMH 
Report No. 290940.17, NPOA Report No. 93-7. 

Henry, W.G 

1 980 Populations and behavior of black brant at Humboldt Bay, California. M.S. thesis, Humboldt State 
University. 107 pp. 

Henson, P. and T.A. Grant 

1 99 1 The effects of human disturbance on trumpeter swan breeding behavior. Wildlife Society Bulletin 

19:248-257. 
- 
Horejsi, B. 

1975 Wildlife studies section III in: Baseline studies of the Biology of streams and wildlife populations in the Sheep creek 

drainage, Alberta. Aquatic Environments, Ltd., Crosslield, Alberta. 



322 



Lisi of References 



Horonjeff, R.D. et al. 

1993 "Acoustic Data Collected at Grand Canyon, Haleakala and Hawaii Volcanoes National Parks," HMMH 
Report No. 290940.18, NPOA Report No. 93-4. 

Jackson, J.A., Schardien, B.J. and T.H. McDaniel 

1977 Opportunistic hunting of a marsh hawk on a bombing range. Raptor Research 1 1 :86. 

Jakimchuk, R.D., De Bock, E., Russell, H. and G. Semenchuk 

1974 A study of the porcupine caribou herd, 1971. Ch. 1 in: Renewable Resources Consulting Services, Ltd., 
Canada Arctic Gas Study, Ltd., Biological Report Series Volume 4. 

Johnson, S.R., Herter, D.R and M.S.W. Bradstreet 

1 987 Habitat use and reproductive success ol pacific eiders Somateria mollissima v-nigra during a period of 
industrial activity. Biological Conservation 41:77-89. 

Kiger,J. 

1970 Helicopter observations of bighorn sheep on the San Andreas National Wildlife Refuge. Transactions, 
Desert Bighorn Council 14:23-27. 

Klein, D.R. 

1973 The reaction of some northern mammals to aircraft disturbance, pp. 377-383 in: Proceedings, Xhh 
International Congress of Game Biologists. National Swedish Environmental Protection Board. Stockholm. 

Krausman, P.R. and J.J. Hervert 

1983 Mountain sheep responses to aerial surveys. Wildlife Society Bulletin 1 1:372-375. 

Krausman, P.R., Leopold, B.D. and D.L. Scarbrough 

1986 Desert mule deer response to aircraft. Wildlife Society Bulletin 14:68-70. 

Kushlan, J.A. 

1979 Effects of helicopter censuses on wading bird colonies. Journal of Wildlife Management 43:756-760. 

Lamp, R.E. 

1 989 Monitoring the effects of military air operations at Fallon Naval Air Station on the biota of Nevada. 
Report by Nevada Dept. of Wildlife for the U.S. Navy. 

Lenarz, M. 

1 974 The reaction of Dall sheep to an FH- 1 1 00 helicopter, in: R.D. Jakimchuk, ed. 77ie reaction of some mammals 
to aircraft and compressor station noise disturbance. Renewable Resources Consulting Services, Ltd. and 
Canadian Arctic Gas Study Ltd. Biological Report Series. Volume 23. 

Linderman, S. 

1972 A report on the sheep study at the Dietrich River headwaters, in: L. Nichols and W. Heimer, eds. Sheep 

Report Vol. 13. Project Progress Report, Federal Aid in Wildlife Restoration Project. W- 17-3 and 

W- 17-4, Alaska Dept. of Fish and Game, Juneau, AK. 

Luz, G.A. and J.B. Smith 

1 976 Reactions of pronghorn antelope to helicopter overflight. Journal of the Acoustical Society of America 
59:1514-1515. 



323 



LIST OF REFERENCES 



Mac Arthur, R.A., Geist, V. and R.H. Johnston 

1982 Cardiac and behavioral responses of mountain sheep to human disturbance. Journal of Wildlife 
Management 46:351-358. 

Mac Arthur, R.A., Johnston, R. and V. Geist 

1979 Factors influencing heart rate in free-ranging bighorn sheep: A physiological approach to the study of 
wildlife harassment. Canadian Journal ot Zoology 57:2010-2021. 

Manning, R. and C. Ciali 

1 980 "Recreation Density and User Satisfaction: A Further Exploration of the Satisfaction Model, "Journal of 
Leisure Research, 12(4), pp 329-345. 

Manning, R. 

1985 Studies in Outdoor Recreation, Oregon State University Press, Corvallis, OR. 

Manci, KM., Gladwin, D.N., Villella, R. and M.G. Cavendish 

1988 Effects of aircraft noise and sonic booms on domestic animals and wildlife: A literature synthesis. 
NERC-88/29. USFWS, National Ecology Research Center, Fort Collins, CO. 88 pp. 

Mattfeld, G. 

1 974 The energetics of winter foraging by white-tailed deer — a perspective on winter. Ph.D. Thesis, State 
University of New York. 306 pp. 

McCourt, K., Feist, J., Doll, D. and J. Russell 

1974 Disturbance studies of caribou and other mammals in the Yukon and Alaska, 1972. Renewable Resources 
Consulting Services, Ltd., Biological Report Series, Vol. 5. 245 pp. 

McCourt, K. and L. Horstman 

1974 The reaction of barren-ground caribou to aircraft. Chapter I in: R. Jakimchuk, ed. Renewable Resources 
Consulting Services, Ltd., Biological Report Series, Vol. 23. 

McCullough, D. 

1969 The rule elk: It's history, behaviour and ecology. University of California Press, Berkeley and Los Angeles. 
209 pp. 

McDonald, CD., Baumgartner, R.M. and R. Iachan 

1994 "National Park Service Visitors Survey," HMMH Report No 290940. 1 2, NPOA Report No. 94-2. 

Miller, F.L. and E. Broughton 

1973 Behavior associated with mortality and stress in maternal-filial pairs of barren-ground caribou. Canadian 
Field Naturalist 87:21-25. 

1 974 Calf mortality on the calving grounds of Kaminuriak caribou during 1 970. Canadian Wildlife Service 
Report Series No. 26, Information Canada, Ottawa. 

Miller, F.L. and A. Gunn 

1 977 A preliminary study of some observable responses by Peary caribou to helicopter induced harassment, 

Prince of Wales Island, Northwest Territories, July- August 1976. Canadian Wildlife Service Progress 

Notes, No. 79. 23 pp. 



324 



List of References 



1979 Responses of Pear)' caribou and muskoxen to helicopter harassment. Canadian Wildlife Service 
Occasional Paper No. 40, Ottawa. 90 pp. 

Nichols, L. 

1972 Productivity in unhunted and heavily-exploited Dall sheep populations, in: L. Nichols and W. Heimer, 
eds. Sheep Report Vol. XIII. Alaska Dept. of Fish and Game, Juneau, AK. 

Miller, N.P. et al. 

1994 "Selecting a Simplified Method for Acoustic Sampling of Aircraft and Background Levels in National 
Parks," HMMH, Lexington, MA, Report No. 290940.24, NPOA Report No. (Unassigned) 

Owens, N. 

1977 Responses of wintering brent geese to human disturbance. Wildfowl 28:5-14. 

Pearson, A.M. 

1975 The northern interior grizzly bear, Ursus arctos L. Canadian Wildlife Service Report Series No. 34. 
Information Canada, Ottawa. 86 pp. 

Piatt, J. B. andC.E. Tull 

1977 A study of wintering and nesting gyrfalcons on the Yukon North Slope during 1975 with emphasis on 
their behaviour during experimental overflights by helicopters, in: W.W. Gunn, C.E. Tull and T.D. 
Wright, eds. Arctic Gas Biological Report Series on Ornithological Studies conducted in the area of the proposed gas 
pipeline route, Northern Alberta, Northwest Territories, Yukon Territory and Alaska, 1975. No. 35. 90 pp. 

Poole, A.F. 

1989 Ospreys: A Natural and Unnatural History. Cambridge University Press, New York. 246 pp. 

Probst, D. and D. Lime. 

1982 "How Satisfying is Satisfaction Research?" Forest and River Recreation: Research Update, University of 
Minnesota Agricultural Experiment Station, Misc. Publication 18. 

Public Law 93-620 

1975 "Grand Canyon National Park Enlargement Act", 93rd Congress of the United States. 

Public Law 100-91 

1 987 "Aircraft Overflights Act", 1 00th Congress of the United States. 

Robert, William E. and N.P. Miller 

1 993 "Audibility by Aircraft Operator and Cumulative Minutes Conversion," Technical Memorandum, (date). 

Reddingius, N.H. 

1994 "User's Manual for the National Park Service Overflight Decision Support System," BBN Report No. 
7984. 

Reid, R.L. and S.C. Miles 

1972 Studies of carbohydrate metabolism in sheep: the adrenal response to psychological stress. Australian 
Journal of Agricultural Resources 1 3 1 :282-295. 



325 



LIST OF REFERENCES 



Ritchie, R.J. 

1987 Response of adult peregrine falcons to experimental and other disturbances along the Trans Alaska 

Pipeline System, Sagavanirktok River, Alaska, 1985, 1986. Report by Alaska Biological Research for 

Alyeska Pipeline Service Company. 

Ruttan, R.A. 

1974 Observations of grizzly bear in the northern Yukon Territory and MacKenzie River Valley, 1972. Chapter 
VII in: R.A. Ruttan and D.R. Wooley, eds. Studies of fur-bearers associated with proposed pipeline routes 
in the Yukon and Northwest Territories. Renewable Resources Consulting Services, Ltd. Biological 
Report Series Vol. 9. 

Salter, R.E. 

1 979 Site utilization, activity budgets, and disturbance responses of Adantic walruses during terrestrial haul-out. 
Canadian Journal of Zoology 57:1 169-1 180. 

Salter, R. and R.A. Davis 

1974 Snow geese disturbance by aircraft on the North Slope, September, 1972. Chapjer VII in: Gunn, W.W. 
and J. A. Livingston, eds. Arctic Gas Biological Report Series Vol. 14. 

Schoepfle, Mark 

1989 ms. Generic Environmental Impact Statement for Low Altitude Flights. 

Schweinsburg, R.E. 

1974a. An ornithological study of proposed gas pipeline routes in Alaska, Yukon Territory and the Northwest 

Territories, 1971. L.G.L. Ltd., Environmental Research Associates, Can. Arctic Gas Study, Ltd. Biological 

Report Series No. 10. 215 pp. 
1914b. Disturbance effects of aircraft to waterfowl on north slope lakes, June, 1972. pp. 1-48 in: Gunn, W.W. 

and J.A. Livingston, eds. Arctic Gas Biological Report Series Vol. 14. 

Schweinsburg, R.E., Gollop, M.A. and R.A. Davis 

1974 Preliminary waterfowl disturbance studies, Mackenzie Valley, August, 1972. Chapter VI in: Gunn, W.W. 
and J.A. Livingston, eds. Arctic Gas Biological Report Series Vol. 14. 

Shandruk, L.J. and K.J. McCormick 

1 989 The relative effectiveness of fixed-wing aircraft and helicopters for surveying trumpeter swans. Canadian 
Wildlife Service Progress Notes: No. 182. 3 pp. 

Slaney, F.F. and Co. Ltd. 

1974 Environmental program, Mackenzie Delta, Northwest Territories, Canada: Winter Study Supplement. 74 
pp. 

Snyder, N.F., Kale, H.W. and P.W. Sykes, Jr. 

1978 An evaluation of some potential impacts of the proposed Dade County Training Jetport on the 
endangered Everglade kite. Florida Audubon Society, Maidand, Florida. 37 pp. 

Spectrum Bird Aircraft Strike Hazard Team 

1994 Bird Aircraft Strike Hazards: Assessing Bird Conflicts. Spectrum Sciences and Software, Inc. 8 pp. 



326 



List of References 



Speich, S.M., Troutman, B.L., Geiger, A.C., Meehan-Martin, P.J. and S.J. Jeffries 

1987 Evaluation of military flight operations on wildlife of the Copalis National Wildlife Refuge, 1984-1985. 
Final Report by Washington Dept. of Game for the U.S. Dept. of the Navy, Western Division. 

Spindler, M.A. 

1 98 3 Distribution, abundance, and productivity of fall staging lesser snow geese in coastal habitats of northeast 
Alaska and northwest Canada, 1983. Alaska National Wildlife Refuge Report No. FY 84-2. 

Stalmaster, M.V. and J.R. Newman 

1 978 Behavioral responses of wintering bald eagles to human activity. Journal of Wildlife Management 
42:506-513. 

Stemp, R. 

1983 Heart rate responses of bighorn sheep to environmental factors and harassment. MS thesis, Faculty of 
Environmental Design, University of Calgary. 

Stockwell, C.A. and G.C. Bateman 

1 987 The impact of helicopter overflights on the foraging behavior of desert bighorn sheep (Ovis canadensis 
nelsoni) at Grand Canyon National Park: Final Report for the National Park Service. 39 pp. 

Stockwell, C.A., Bateman, G.C. and J. Berger 

1 99 1 Conflicts in National Parks: A case study of helicopters and bighorn sheep time budgets at the Grand 
Canyon. Biological Conservation 56:317-328. 

Summerfield, B. and D. Klein 

1974 Population dynamics and seasonal movement patterns of Dall sheep in the Atigun River Canyon area, 
Brooks Range, Alaska. M.S. Thesis, Univ. of Alaska, Fairbanks. 

Surrendi, D.C. and E.A. DeBock 

1976 Seasonal distribution, population status and behaviour of the Porcupine Caribou herd. Canada Wildlife 
Service, Mackenzie Valley Pipeline investigations, Ottawa. 144 pp. 

Sutherland, Louis C, Brown, R., and D. Goerner 

1990 "Evaluation of Potential Damage to Unconventional Structures by Sonic Booms," Report No. 

HSD-TR-90-02 1, U.S. Air Force, Human Systems Division, Noise & Sonic Boom Impact Technology 

Program, Wright- Patterson AFB, OH 

Tabachnick, B.G., et al. 

1992 "Estimation of Aircraft Overflight Exposure in National Parks and Forest Service Wildernesses," BBN 
Report No. 7259, NPOA Report No. 92- 1 . 

Takekawa, J.E. 

1987 Memorandum, USFWS to D. Gladwin re: Effects of aircraft noise and sonic booms on fish and wildlife. 

United States Department of Agriculture, Forest Service 

1979 "Density , Crowding and Satisfaction: Sociological Studies for Determining Carrying Capacities," 
Proceedings: River Recreation Management and Research Symposium, Technical Report NC-28. 



327 



LIST OF REFERENCES 



United States Department oi Interior, Fish and Wildlife Service 

1993 Aircraft overflight issues on national wildlife refuges. Compilation of reports from national wildlife refuges. 

United States Department of Interior, National Park Service 

1988 Management Policies: U.S. Department of Interior, National Park Service. 

1988 Management Policies, Chapter 4 

1 990 NPS-77, Natural Resource Management Guidelines, National Park Service. 

Valkenburg, P. and J.L. Davis 

1985 The reaction of caribou to aircraft: a comparison of two herds, pp. 7-9 in: Martell, A.M. and D.E. Russell, 
eds. Caribou and human activity. Proceedings, 1st North American Caribou Workshop, Whitehorse, Yukon. 1983. 

Vaske, J., Fedler, A. and A. Graefe 

1986 "Multiple Determinants of Satisfaction from a Specific Waterfowl Hunting Trip," Leisure Sciences, 8(2), pp 
149-166. 

Ward, D. and R. Stehn 

1 989 Response of brant and other geese to aircraft disturbances at Izembek Lagoon, Alaska. USFWS Alaska 
Fish and Wildlife Research Center, Anchorage. 241 pp. 

Ward, J.L. 

1972 Prenatal stress feminizes and demasculinizes the behavior of males. Science 175:82-84 

Ward, J. and P. L. Sharp 

1974 Effects of aircraft disturbance on moulting sea ducks at Herschel Island, Yukon Territory, August 8 1973. 
Chapter II in: Gunn, W.W., Richardson, W.J., Schweinsburg, R.E. and T.D. Wright, eds. Studies on 
Terrestrial Bird Populations, moulting Sea Ducks and bird Productivity in the Western Arctic, 1973. Arctic Gas 
Biological Report Series, Vol. 29. 

White, CM. and S.K. Sherrod 

1973 Advantages and disadvantages of the use of rotor-winged aircraft in raptor surveys. Raptor Research 
7:97-104. 

White, C.W. and T.L. Thurow 

1 985 Reproduction of ferruginous hawks exposed to controlled disturbance. Condor 87: 1 4-22. 

Williams, D. 

1988 "Great Expectations and the Limits to Satisfaction: A Review of Recreation and Consumer Satisfaction 

Research," Outdoor Recreation Benchmark: Proceedings of the National Outdoor Recreation Forum, USDA General 

Technical Report SE-52. 

Workman, G.W., Bunch, T.D., Call, J.W., Evans, R.C., Nielson, L.S. and E.M. Rawlings 

1992a. Sonic boom and other disturbance impacts on pronghorn antelope (Antilocapra americana). Utah State 

University for Hill Air Force Base, Utah. 
19926. Sonic boom and other disturbance impacts on bighorn sheep (Ovis canadensis). Utah State University for 

Hill Air Force Base, Utah. 
1992c. Sonic boom and other disturbance impacts on Rocky mountain elk (Cervis canadensis). Utah State 

University for Hill Air Force Base, Utah. 



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As the nation's principal conservation agency, the Department of the Interior has responsibility for most of our 
nationally owned public lands and natural resources. This includes fostering sound use of our land and water 
resources; protecting our fish, wildlife, and biological diversity; preserving the environmental and cultural 
values of our national parks and historical places; and providing for the enjoyment of life through outdoor 
recreation. The department assesses our energy and mineral resources and works to ensure that their 
development is in the best interests of all our people by encouraging stewardship and citizen participation in 
their care. The department also has a major responsibility for American Indian reservation communities and for 
people who live in island territories under U.S. administration. 

Publication services were provided by the Branch of Publications and Graphic Design of the Denver Service 
Center. 



NPSD-1062 July 1995 



United States Department of the Interior / National Park Service